//
// Created by Admin on 2021/4/13.
//
#include "stb_image.h"
#ifndef STBI_NO_HDR
#include <math.h>  // ldexp
#include <string.h> // strcmp
#endif

#ifndef STBI_NO_STDIO
#include <stdio.h>
#endif
#include <stdlib.h>
#include <memory.h>
#include <assert.h>
#include <stdarg.h>


#ifndef _MSC_VER
#ifdef __cplusplus
#define __forceinline inline
#else
#define __forceinline
#endif
#endif


// implementation:
typedef unsigned char uint8;
typedef unsigned short uint16;
typedef   signed short  int16;
typedef unsigned int   uint32;
typedef   signed int    int32;
typedef unsigned int   uint;

// should produce compiler error if size is wrong
typedef unsigned char validate_uint32[sizeof(uint32)==4];

#if defined(STBI_NO_STDIO) && !defined(STBI_NO_WRITE)
#define STBI_NO_WRITE
#endif

//////////////////////////////////////////////////////////////////////////////
//
// Generic API that works on all image types
//

// this is not threadsafe
static char *failure_reason;

char *stbi_failure_reason(void)
{
    return failure_reason;
}

static int e(const char *str)
{
    failure_reason = (char *)str;
    return 0;
}

#ifdef STBI_NO_FAILURE_STRINGS
#define e(x,y)  0
#elif defined(STBI_FAILURE_USERMSG)
#define e(x,y)  e(y)
#else
#define e(x,y)  e(x)
#endif

#define epf(x,y)   ((float *) (e(x,y)?NULL:NULL))
#define epuc(x,y)  ((unsigned char *) (e(x,y)?NULL:NULL))

void stbi_image_free(void *retval_from_stbi_load)
{
    free(retval_from_stbi_load);
}

#define MAX_LOADERS  32
stbi_loader *loaders[MAX_LOADERS];
static int max_loaders = 0;

int stbi_register_loader(stbi_loader *loader)
{
    int i;
    for (i=0; i < MAX_LOADERS; ++i) {
        // already present?
        if (loaders[i] == loader)
            return 1;
        // end of the list?
        if (loaders[i] == NULL) {
            loaders[i] = loader;
            max_loaders = i+1;
            return 1;
        }
    }
    // no room for it
    return 0;
}

#ifndef STBI_NO_HDR
static float   *ldr_to_hdr(stbi_uc *data, int x, int y, int comp);
static stbi_uc *hdr_to_ldr(float   *data, int x, int y, int comp);
#endif

#ifndef STBI_NO_STDIO
unsigned char *stbi_load(char const *filename, int *x, int *y, int *comp, int req_comp)
{
    FILE *f = fopen(filename, "rb");
    unsigned char *result;
    if (!f) return epuc("can't fopen", "Unable to open file");
    result = stbi_load_from_file(f,x,y,comp,req_comp);
    fclose(f);
    return result;
}

unsigned char *stbi_load_from_file(FILE *f, int *x, int *y, int *comp, int req_comp)
{
    int i;
    if (stbi_jpeg_test_file(f))
        return stbi_jpeg_load_from_file(f,x,y,comp,req_comp);
    if (stbi_png_test_file(f))
        return stbi_png_load_from_file(f,x,y,comp,req_comp);
    if (stbi_bmp_test_file(f))
        return stbi_bmp_load_from_file(f,x,y,comp,req_comp);
    if (stbi_psd_test_file(f))
        return stbi_psd_load_from_file(f,x,y,comp,req_comp);
#ifndef STBI_NO_HDR
    if (stbi_hdr_test_file(f)) {
        float *hdr = stbi_hdr_load_from_file(f, x,y,comp,req_comp);
        return hdr_to_ldr(hdr, *x, *y, req_comp ? req_comp : *comp);
    }
#endif
    for (i=0; i < max_loaders; ++i)
        if (loaders[i]->test_file(f))
            return loaders[i]->load_from_file(f,x,y,comp,req_comp);
    // test tga last because it's a crappy test!
    if (stbi_tga_test_file(f))
        return stbi_tga_load_from_file(f,x,y,comp,req_comp);
    return epuc("unknown image type", "Image not of any known type, or corrupt");
}
#endif

unsigned char *stbi_load_from_memory(stbi_uc const *buffer, int len, int *x, int *y, int *comp, int req_comp)
{
    int i;
    if (stbi_jpeg_test_memory(buffer,len))
        return stbi_jpeg_load_from_memory(buffer,len,x,y,comp,req_comp);
    if (stbi_png_test_memory(buffer,len))
        return stbi_png_load_from_memory(buffer,len,x,y,comp,req_comp);
    if (stbi_bmp_test_memory(buffer,len))
        return stbi_bmp_load_from_memory(buffer,len,x,y,comp,req_comp);
    if (stbi_psd_test_memory(buffer,len))
        return stbi_psd_load_from_memory(buffer,len,x,y,comp,req_comp);
#ifndef STBI_NO_HDR
    if (stbi_hdr_test_memory(buffer, len)) {
        float *hdr = stbi_hdr_load_from_memory(buffer, len,x,y,comp,req_comp);
        return hdr_to_ldr(hdr, *x, *y, req_comp ? req_comp : *comp);
    }
#endif
    for (i=0; i < max_loaders; ++i)
        if (loaders[i]->test_memory(buffer,len))
            return loaders[i]->load_from_memory(buffer,len,x,y,comp,req_comp);
    // test tga last because it's a crappy test!
    if (stbi_tga_test_memory(buffer,len))
        return stbi_tga_load_from_memory(buffer,len,x,y,comp,req_comp);
    return epuc("unknown image type", "Image not of any known type, or corrupt");
}

#ifndef STBI_NO_HDR

#ifndef STBI_NO_STDIO
float *stbi_loadf(char const *filename, int *x, int *y, int *comp, int req_comp)
{
    FILE *f = fopen(filename, "rb");
    float *result;
    if (!f) return epf("can't fopen", "Unable to open file");
    result = stbi_loadf_from_file(f,x,y,comp,req_comp);
    fclose(f);
    return result;
}

float *stbi_loadf_from_file(FILE *f, int *x, int *y, int *comp, int req_comp)
{
    unsigned char *data;
#ifndef STBI_NO_HDR
    if (stbi_hdr_test_file(f))
        return stbi_hdr_load_from_file(f,x,y,comp,req_comp);
#endif
    data = stbi_load_from_file(f, x, y, comp, req_comp);
    if (data)
        return ldr_to_hdr(data, *x, *y, req_comp ? req_comp : *comp);
    return epf("unknown image type", "Image not of any known type, or corrupt");
}
#endif

float *stbi_loadf_from_memory(stbi_uc const *buffer, int len, int *x, int *y, int *comp, int req_comp)
{
    stbi_uc *data;
#ifndef STBI_NO_HDR
    if (stbi_hdr_test_memory(buffer, len))
        return stbi_hdr_load_from_memory(buffer, len,x,y,comp,req_comp);
#endif
    data = stbi_load_from_memory(buffer, len, x, y, comp, req_comp);
    if (data)
        return ldr_to_hdr(data, *x, *y, req_comp ? req_comp : *comp);
    return epf("unknown image type", "Image not of any known type, or corrupt");
}
#endif

// these is-hdr-or-not is defined independent of whether STBI_NO_HDR is
// defined, for API simplicity; if STBI_NO_HDR is defined, it always
// reports false!

int stbi_is_hdr_from_memory(stbi_uc const *buffer, int len)
{
#ifndef STBI_NO_HDR
    return stbi_hdr_test_memory(buffer, len);
#else
    return 0;
#endif
}

#ifndef STBI_NO_STDIO
extern int      stbi_is_hdr          (char const *filename)
{
    FILE *f = fopen(filename, "rb");
    int result=0;
    if (f) {
        result = stbi_is_hdr_from_file(f);
        fclose(f);
    }
    return result;
}

extern int      stbi_is_hdr_from_file(FILE *f)
{
#ifndef STBI_NO_HDR
    return stbi_hdr_test_file(f);
#else
    return 0;
#endif
}

#endif

// @TODO: get image dimensions & components without fully decoding
#ifndef STBI_NO_STDIO
extern int      stbi_info            (char const *filename,           int *x, int *y, int *comp);
extern int      stbi_info_from_file  (FILE *f,                  int *x, int *y, int *comp);
#endif
extern int      stbi_info_from_memory(stbi_uc const *buffer, int len, int *x, int *y, int *comp);

#ifndef STBI_NO_HDR
static float h2l_gamma_i=1.0f/2.2f, h2l_scale_i=1.0f;
static float l2h_gamma=2.2f, l2h_scale=1.0f;

void   stbi_hdr_to_ldr_gamma(float gamma) { h2l_gamma_i = 1/gamma; }
void   stbi_hdr_to_ldr_scale(float scale) { h2l_scale_i = 1/scale; }

void   stbi_ldr_to_hdr_gamma(float gamma) { l2h_gamma = gamma; }
void   stbi_ldr_to_hdr_scale(float scale) { l2h_scale = scale; }
#endif


//////////////////////////////////////////////////////////////////////////////
//
// Common code used by all image loaders
//

enum
{
    SCAN_load=0,
    SCAN_type,
    SCAN_header
};

typedef struct
{
    uint32 img_x, img_y;
    int img_n, img_out_n;

#ifndef STBI_NO_STDIO
    FILE  *img_file;
#endif
    uint8 *img_buffer, *img_buffer_end;
} stbi;

#ifndef STBI_NO_STDIO
static void start_file(stbi *s, FILE *f)
{
    s->img_file = f;
}
#endif

static void start_mem(stbi *s, uint8 const *buffer, int len)
{
#ifndef STBI_NO_STDIO
    s->img_file = NULL;
#endif
    s->img_buffer = (uint8 *) buffer;
    s->img_buffer_end = (uint8 *) buffer+len;
}

__forceinline static int get8(stbi *s)
{
#ifndef STBI_NO_STDIO
    if (s->img_file) {
        int c = fgetc(s->img_file);
        return c == EOF ? 0 : c;
    }
#endif
    if (s->img_buffer < s->img_buffer_end)
        return *s->img_buffer++;
    return 0;
}

__forceinline static int at_eof(stbi *s)
{
#ifndef STBI_NO_STDIO
    if (s->img_file)
        return feof(s->img_file);
#endif
    return s->img_buffer >= s->img_buffer_end;
}

__forceinline static uint8 get8u(stbi *s)
{
    return (uint8) get8(s);
}

static void skip(stbi *s, int n)
{
#ifndef STBI_NO_STDIO
    if (s->img_file)
        fseek(s->img_file, n, SEEK_CUR);
    else
#endif
        s->img_buffer += n;
}

static int get16(stbi *s)
{
    int z = get8(s);
    return (z << 8) + get8(s);
}

static uint32 get32(stbi *s)
{
    uint32 z = get16(s);
    return (z << 16) + get16(s);
}

static int get16le(stbi *s)
{
    int z = get8(s);
    return z + (get8(s) << 8);
}

static uint32 get32le(stbi *s)
{
    uint32 z = get16le(s);
    return z + (get16le(s) << 16);
}

static void getn(stbi *s, stbi_uc *buffer, int n)
{
#ifndef STBI_NO_STDIO
    if (s->img_file) {
        fread(buffer, 1, n, s->img_file);
        return;
    }
#endif
    memcpy(buffer, s->img_buffer, n);
    s->img_buffer += n;
}

//////////////////////////////////////////////////////////////////////////////
//
//  generic converter from built-in img_n to req_comp
//    individual types do this automatically as much as possible (e.g. jpeg
//    does all cases internally since it needs to colorspace convert anyway,
//    and it never has alpha, so very few cases ). png can automatically
//    interleave an alpha=255 channel, but falls back to this for other cases
//
//  assume data buffer is malloced, so malloc a new one and free that one
//  only failure mode is malloc failing

static uint8 compute_y(int r, int g, int b)
{
    return (uint8) (((r*77) + (g*150) +  (29*b)) >> 8);
}

static unsigned char *convert_format(unsigned char *data, int img_n, int req_comp, uint x, uint y)
{
    int i,j;
    unsigned char *good;

    if (req_comp == img_n) return data;
    assert(req_comp >= 1 && req_comp <= 4);

    good = (unsigned char *) malloc(req_comp * x * y);
    if (good == NULL) {
        free(data);
        return epuc("outofmem", "Out of memory");
    }

    for (j=0; j < (int) y; ++j) {
        unsigned char *src  = data + j * x * img_n   ;
        unsigned char *dest = good + j * x * req_comp;

#define COMBO(a,b)  ((a)*8+(b))
#define CASE(a,b)   case COMBO(a,b): for(i=x-1; i >= 0; --i, src += a, dest += b)
        // convert source image with img_n components to one with req_comp components;
        // avoid switch per pixel, so use switch per scanline and massive macros
        switch(COMBO(img_n, req_comp)) {
            CASE(1,2) dest[0]=src[0], dest[1]=255; break;
            CASE(1,3) dest[0]=dest[1]=dest[2]=src[0]; break;
            CASE(1,4) dest[0]=dest[1]=dest[2]=src[0], dest[3]=255; break;
            CASE(2,1) dest[0]=src[0]; break;
            CASE(2,3) dest[0]=dest[1]=dest[2]=src[0]; break;
            CASE(2,4) dest[0]=dest[1]=dest[2]=src[0], dest[3]=src[1]; break;
            CASE(3,4) dest[0]=src[0],dest[1]=src[1],dest[2]=src[2],dest[3]=255; break;
            CASE(3,1) dest[0]=compute_y(src[0],src[1],src[2]); break;
            CASE(3,2) dest[0]=compute_y(src[0],src[1],src[2]), dest[1] = 255; break;
            CASE(4,1) dest[0]=compute_y(src[0],src[1],src[2]); break;
            CASE(4,2) dest[0]=compute_y(src[0],src[1],src[2]), dest[1] = src[3]; break;
            CASE(4,3) dest[0]=src[0],dest[1]=src[1],dest[2]=src[2]; break;
            default: assert(0);
        }
#undef CASE
    }

    free(data);
    return good;
}

#ifndef STBI_NO_HDR
static float   *ldr_to_hdr(stbi_uc *data, int x, int y, int comp)
{
    int i,k,n;
    float *output = (float *) malloc(x * y * comp * sizeof(float));
    if (output == NULL) { free(data); return epf("outofmem", "Out of memory"); }
    // compute number of non-alpha components
    if (comp & 1) n = comp; else n = comp-1;
    for (i=0; i < x*y; ++i) {
        for (k=0; k < n; ++k) {
            output[i*comp + k] = (float) pow(data[i*comp+k]/255.0f, l2h_gamma) * l2h_scale;
        }
        if (k < comp) output[i*comp + k] = data[i*comp+k]/255.0f;
    }
    free(data);
    return output;
}

#define float2int(x)   ((int) (x))
static stbi_uc *hdr_to_ldr(float   *data, int x, int y, int comp)
{
    int i,k,n;
    stbi_uc *output = (stbi_uc *) malloc(x * y * comp);
    if (output == NULL) { free(data); return epuc("outofmem", "Out of memory"); }
    // compute number of non-alpha components
    if (comp & 1) n = comp; else n = comp-1;
    for (i=0; i < x*y; ++i) {
        for (k=0; k < n; ++k) {
            float z = (float) pow(data[i*comp+k]*h2l_scale_i, h2l_gamma_i) * 255 + 0.5f;
            if (z < 0) z = 0;
            if (z > 255) z = 255;
            output[i*comp + k] = (stbi_uc)float2int(z);
        }
        if (k < comp) {
            float z = data[i*comp+k] * 255 + 0.5f;
            if (z < 0) z = 0;
            if (z > 255) z = 255;
            output[i*comp + k] = (stbi_uc)float2int(z);
        }
    }
    free(data);
    return output;
}
#endif

//////////////////////////////////////////////////////////////////////////////
//
//  "baseline" JPEG/JFIF decoder (not actually fully baseline implementation)
//
//    simple implementation
//      - channel subsampling of at most 2 in each dimension
//      - doesn't support delayed output of y-dimension
//      - simple interface (only one output format: 8-bit interleaved RGB)
//      - doesn't try to recover corrupt jpegs
//      - doesn't allow partial loading, loading multiple at once
//      - still fast on x86 (copying globals into locals doesn't help x86)
//      - allocates lots of intermediate memory (full size of all components)
//        - non-interleaved case requires this anyway
//        - allows good upsampling (see next)
//    high-quality
//      - upsampled channels are bilinearly interpolated, even across blocks
//      - quality integer IDCT derived from IJG's 'slow'
//    performance
//      - fast huffman; reasonable integer IDCT
//      - uses a lot of intermediate memory, could cache poorly
//      - load http://nothings.org/remote/anemones.jpg 3 times on 2.8Ghz P4
//          stb_jpeg:   1.34 seconds (MSVC6, default release build)
//          stb_jpeg:   1.06 seconds (MSVC6, processor = Pentium Pro)
//          IJL11.dll:  1.08 seconds (compiled by intel)
//          IJG 1998:   0.98 seconds (MSVC6, makefile provided by IJG)
//          IJG 1998:   0.95 seconds (MSVC6, makefile + proc=PPro)

// huffman decoding acceleration
#define FAST_BITS   9  // larger handles more cases; smaller stomps less cache

typedef struct
{
    uint8  fast[1 << FAST_BITS];
    // weirdly, repacking this into AoS is a 10% speed loss, instead of a win
    uint16 code[256];
    uint8  values[256];
    uint8  size[257];
    unsigned int maxcode[18];
    int    delta[17];   // old 'firstsymbol' - old 'firstcode'
} huffman;

typedef struct
{
#if STBI_SIMD
    unsigned short dequant2[4][64];
#endif
    stbi s;
    huffman huff_dc[4];
    huffman huff_ac[4];
    uint8 dequant[4][64];

// sizes for components, interleaved MCUs
    int img_h_max, img_v_max;
    int img_mcu_x, img_mcu_y;
    int img_mcu_w, img_mcu_h;

// definition of jpeg image component
    struct
    {
        int id;
        int h,v;
        int tq;
        int hd,ha;
        int dc_pred;

        int x,y,w2,h2;
        uint8 *data;
        void *raw_data;
        uint8 *linebuf;
    } img_comp[4];

    uint32         code_buffer; // jpeg entropy-coded buffer
    int            code_bits;   // number of valid bits
    unsigned char  marker;      // marker seen while filling entropy buffer
    int            nomore;      // flag if we saw a marker so must stop

    int scan_n, order[4];
    int restart_interval, todo;
} jpeg;

static int build_huffman(huffman *h, int *count)
{
    int i,j,k=0,code;
    // build size list for each symbol (from JPEG spec)
    for (i=0; i < 16; ++i)
        for (j=0; j < count[i]; ++j)
            h->size[k++] = (uint8) (i+1);
    h->size[k] = 0;

    // compute actual symbols (from jpeg spec)
    code = 0;
    k = 0;
    for(j=1; j <= 16; ++j) {
        // compute delta to add to code to compute symbol id
        h->delta[j] = k - code;
        if (h->size[k] == j) {
            while (h->size[k] == j)
                h->code[k++] = (uint16) (code++);
            if (code-1 >= (1 << j)) return e("bad code lengths","Corrupt JPEG");
        }
        // compute largest code + 1 for this size, preshifted as needed later
        h->maxcode[j] = code << (16-j);
        code <<= 1;
    }
    h->maxcode[j] = 0xffffffff;

    // build non-spec acceleration table; 255 is flag for not-accelerated
    memset(h->fast, 255, 1 << FAST_BITS);
    for (i=0; i < k; ++i) {
        int s = h->size[i];
        if (s <= FAST_BITS) {
            int c = h->code[i] << (FAST_BITS-s);
            int m = 1 << (FAST_BITS-s);
            for (j=0; j < m; ++j) {
                h->fast[c+j] = (uint8) i;
            }
        }
    }
    return 1;
}

static void grow_buffer_unsafe(jpeg *j)
{
    do {
        int b = j->nomore ? 0 : get8(&j->s);
        if (b == 0xff) {
            int c = get8(&j->s);
            if (c != 0) {
                j->marker = (unsigned char) c;
                j->nomore = 1;
                return;
            }
        }
        j->code_buffer = (j->code_buffer << 8) | b;
        j->code_bits += 8;
    } while (j->code_bits <= 24);
}

// (1 << n) - 1
static uint32 bmask[17]={0,1,3,7,15,31,63,127,255,511,1023,2047,4095,8191,16383,32767,65535};

// decode a jpeg huffman value from the bitstream
__forceinline static int decode(jpeg *j, huffman *h)
{
    unsigned int temp;
    int c,k;

    if (j->code_bits < 16) grow_buffer_unsafe(j);

    // look at the top FAST_BITS and determine what symbol ID it is,
    // if the code is <= FAST_BITS
    c = (j->code_buffer >> (j->code_bits - FAST_BITS)) & ((1 << FAST_BITS)-1);
    k = h->fast[c];
    if (k < 255) {
        if (h->size[k] > j->code_bits)
            return -1;
        j->code_bits -= h->size[k];
        return h->values[k];
    }

    // naive test is to shift the code_buffer down so k bits are
    // valid, then test against maxcode. To speed this up, we've
    // preshifted maxcode left so that it has (16-k) 0s at the
    // end; in other words, regardless of the number of bits, it
    // wants to be compared against something shifted to have 16;
    // that way we don't need to shift inside the loop.
    if (j->code_bits < 16)
        temp = (j->code_buffer << (16 - j->code_bits)) & 0xffff;
    else
        temp = (j->code_buffer >> (j->code_bits - 16)) & 0xffff;
    for (k=FAST_BITS+1 ; ; ++k)
        if (temp < h->maxcode[k])
            break;
    if (k == 17) {
        // error! code not found
        j->code_bits -= 16;
        return -1;
    }

    if (k > j->code_bits)
        return -1;

    // convert the huffman code to the symbol id
    c = ((j->code_buffer >> (j->code_bits - k)) & bmask[k]) + h->delta[k];
    assert((((j->code_buffer) >> (j->code_bits - h->size[c])) & bmask[h->size[c]]) == h->code[c]);

    // convert the id to a symbol
    j->code_bits -= k;
    return h->values[c];
}

// combined JPEG 'receive' and JPEG 'extend', since baseline
// always extends everything it receives.
__forceinline static int extend_receive(jpeg *j, int n)
{
    unsigned int m = 1 << (n-1);
    unsigned int k;
    if (j->code_bits < n) grow_buffer_unsafe(j);
    k = (j->code_buffer >> (j->code_bits - n)) & bmask[n];
    j->code_bits -= n;
    // the following test is probably a random branch that won't
    // predict well. I tried to table accelerate it but failed.
    // maybe it's compiling as a conditional move?
    if (k < m)
        return (-1 << n) + k + 1;
    else
        return k;
}

// given a value that's at position X in the zigzag stream,
// where does it appear in the 8x8 matrix coded as row-major?
static uint8 dezigzag[64+15] =
        {
                0,  1,  8, 16,  9,  2,  3, 10,
                17, 24, 32, 25, 18, 11,  4,  5,
                12, 19, 26, 33, 40, 48, 41, 34,
                27, 20, 13,  6,  7, 14, 21, 28,
                35, 42, 49, 56, 57, 50, 43, 36,
                29, 22, 15, 23, 30, 37, 44, 51,
                58, 59, 52, 45, 38, 31, 39, 46,
                53, 60, 61, 54, 47, 55, 62, 63,
                // let corrupt input sample past end
                63, 63, 63, 63, 63, 63, 63, 63,
                63, 63, 63, 63, 63, 63, 63
        };

// decode one 64-entry block--
static int decode_block(jpeg *j, short data[64], huffman *hdc, huffman *hac, int b)
{
    int diff,dc,k;
    int t = decode(j, hdc);
    if (t < 0) return e("bad huffman code","Corrupt JPEG");

    // 0 all the ac values now so we can do it 32-bits at a time
    memset(data,0,64*sizeof(data[0]));

    diff = t ? extend_receive(j, t) : 0;
    dc = j->img_comp[b].dc_pred + diff;
    j->img_comp[b].dc_pred = dc;
    data[0] = (short) dc;

    // decode AC components, see JPEG spec
    k = 1;
    do {
        int r,s;
        int rs = decode(j, hac);
        if (rs < 0) return e("bad huffman code","Corrupt JPEG");
        s = rs & 15;
        r = rs >> 4;
        if (s == 0) {
            if (rs != 0xf0) break; // end block
            k += 16;
        } else {
            k += r;
            // decode into unzigzag'd location
            data[dezigzag[k++]] = (short) extend_receive(j,s);
        }
    } while (k < 64);
    return 1;
}

// take a -128..127 value and clamp it and convert to 0..255
__forceinline static uint8 clamp(int x)
{
    x += 128;
    // trick to use a single test to catch both cases
    if ((unsigned int) x > 255) {
        if (x < 0) return 0;
        if (x > 255) return 255;
    }
    return (uint8) x;
}

#define f2f(x)  (int) (((x) * 4096 + 0.5))
#define fsh(x)  ((x) << 12)

// derived from jidctint -- DCT_ISLOW
#define IDCT_1D(s0,s1,s2,s3,s4,s5,s6,s7)       \
   int t0,t1,t2,t3,p1,p2,p3,p4,p5,x0,x1,x2,x3; \
   p2 = s2;                                    \
   p3 = s6;                                    \
   p1 = (p2+p3) * f2f(0.5411961f);             \
   t2 = p1 + p3*f2f(-1.847759065f);            \
   t3 = p1 + p2*f2f( 0.765366865f);            \
   p2 = s0;                                    \
   p3 = s4;                                    \
   t0 = fsh(p2+p3);                            \
   t1 = fsh(p2-p3);                            \
   x0 = t0+t3;                                 \
   x3 = t0-t3;                                 \
   x1 = t1+t2;                                 \
   x2 = t1-t2;                                 \
   t0 = s7;                                    \
   t1 = s5;                                    \
   t2 = s3;                                    \
   t3 = s1;                                    \
   p3 = t0+t2;                                 \
   p4 = t1+t3;                                 \
   p1 = t0+t3;                                 \
   p2 = t1+t2;                                 \
   p5 = (p3+p4)*f2f( 1.175875602f);            \
   t0 = t0*f2f( 0.298631336f);                 \
   t1 = t1*f2f( 2.053119869f);                 \
   t2 = t2*f2f( 3.072711026f);                 \
   t3 = t3*f2f( 1.501321110f);                 \
   p1 = p5 + p1*f2f(-0.899976223f);            \
   p2 = p5 + p2*f2f(-2.562915447f);            \
   p3 = p3*f2f(-1.961570560f);                 \
   p4 = p4*f2f(-0.390180644f);                 \
   t3 += p1+p4;                                \
   t2 += p2+p3;                                \
   t1 += p2+p4;                                \
   t0 += p1+p3;

#if !STBI_SIMD
// .344 seconds on 3*anemones.jpg
static void idct_block(uint8 *out, int out_stride, short data[64], uint8 *dequantize)
{
    int i,val[64],*v=val;
    uint8 *o,*dq = dequantize;
    short *d = data;

    // columns
    for (i=0; i < 8; ++i,++d,++dq, ++v) {
        // if all zeroes, shortcut -- this avoids dequantizing 0s and IDCTing
        if (d[ 8]==0 && d[16]==0 && d[24]==0 && d[32]==0
            && d[40]==0 && d[48]==0 && d[56]==0) {
            //    no shortcut                 0     seconds
            //    (1|2|3|4|5|6|7)==0          0     seconds
            //    all separate               -0.047 seconds
            //    1 && 2|3 && 4|5 && 6|7:    -0.047 seconds
            int dcterm = d[0] * dq[0] << 2;
            v[0] = v[8] = v[16] = v[24] = v[32] = v[40] = v[48] = v[56] = dcterm;
        } else {
            IDCT_1D(d[ 0]*dq[ 0],d[ 8]*dq[ 8],d[16]*dq[16],d[24]*dq[24],
                    d[32]*dq[32],d[40]*dq[40],d[48]*dq[48],d[56]*dq[56])
            // constants scaled things up by 1<<12; let's bring them back
            // down, but keep 2 extra bits of precision
            x0 += 512; x1 += 512; x2 += 512; x3 += 512;
            v[ 0] = (x0+t3) >> 10;
            v[56] = (x0-t3) >> 10;
            v[ 8] = (x1+t2) >> 10;
            v[48] = (x1-t2) >> 10;
            v[16] = (x2+t1) >> 10;
            v[40] = (x2-t1) >> 10;
            v[24] = (x3+t0) >> 10;
            v[32] = (x3-t0) >> 10;
        }
    }

    for (i=0, v=val, o=out; i < 8; ++i,v+=8,o+=out_stride) {
        // no fast case since the first 1D IDCT spread components out
        IDCT_1D(v[0],v[1],v[2],v[3],v[4],v[5],v[6],v[7])
        // constants scaled things up by 1<<12, plus we had 1<<2 from first
        // loop, plus horizontal and vertical each scale by sqrt(8) so together
        // we've got an extra 1<<3, so 1<<17 total we need to remove.
        x0 += 65536; x1 += 65536; x2 += 65536; x3 += 65536;
        o[0] = clamp((x0+t3) >> 17);
        o[7] = clamp((x0-t3) >> 17);
        o[1] = clamp((x1+t2) >> 17);
        o[6] = clamp((x1-t2) >> 17);
        o[2] = clamp((x2+t1) >> 17);
        o[5] = clamp((x2-t1) >> 17);
        o[3] = clamp((x3+t0) >> 17);
        o[4] = clamp((x3-t0) >> 17);
    }
}
#else
static void idct_block(uint8 *out, int out_stride, short data[64], unsigned short *dequantize)
{
   int i,val[64],*v=val;
   uint8 *o;
   unsigned short *dq = dequantize;
   short *d = data;

   // columns
   for (i=0; i < 8; ++i,++d,++dq, ++v) {
      // if all zeroes, shortcut -- this avoids dequantizing 0s and IDCTing
      if (d[ 8]==0 && d[16]==0 && d[24]==0 && d[32]==0
           && d[40]==0 && d[48]==0 && d[56]==0) {
         //    no shortcut                 0     seconds
         //    (1|2|3|4|5|6|7)==0          0     seconds
         //    all separate               -0.047 seconds
         //    1 && 2|3 && 4|5 && 6|7:    -0.047 seconds
         int dcterm = d[0] * dq[0] << 2;
         v[0] = v[8] = v[16] = v[24] = v[32] = v[40] = v[48] = v[56] = dcterm;
      } else {
         IDCT_1D(d[ 0]*dq[ 0],d[ 8]*dq[ 8],d[16]*dq[16],d[24]*dq[24],
                 d[32]*dq[32],d[40]*dq[40],d[48]*dq[48],d[56]*dq[56])
         // constants scaled things up by 1<<12; let's bring them back
         // down, but keep 2 extra bits of precision
         x0 += 512; x1 += 512; x2 += 512; x3 += 512;
         v[ 0] = (x0+t3) >> 10;
         v[56] = (x0-t3) >> 10;
         v[ 8] = (x1+t2) >> 10;
         v[48] = (x1-t2) >> 10;
         v[16] = (x2+t1) >> 10;
         v[40] = (x2-t1) >> 10;
         v[24] = (x3+t0) >> 10;
         v[32] = (x3-t0) >> 10;
      }
   }

   for (i=0, v=val, o=out; i < 8; ++i,v+=8,o+=out_stride) {
      // no fast case since the first 1D IDCT spread components out
      IDCT_1D(v[0],v[1],v[2],v[3],v[4],v[5],v[6],v[7])
      // constants scaled things up by 1<<12, plus we had 1<<2 from first
      // loop, plus horizontal and vertical each scale by sqrt(8) so together
      // we've got an extra 1<<3, so 1<<17 total we need to remove.
      x0 += 65536; x1 += 65536; x2 += 65536; x3 += 65536;
      o[0] = clamp((x0+t3) >> 17);
      o[7] = clamp((x0-t3) >> 17);
      o[1] = clamp((x1+t2) >> 17);
      o[6] = clamp((x1-t2) >> 17);
      o[2] = clamp((x2+t1) >> 17);
      o[5] = clamp((x2-t1) >> 17);
      o[3] = clamp((x3+t0) >> 17);
      o[4] = clamp((x3-t0) >> 17);
   }
}
static stbi_idct_8x8 stbi_idct_installed = idct_block;

extern void stbi_install_idct(stbi_idct_8x8 func)
{
   stbi_idct_installed = func;
}
#endif

#define MARKER_none  0xff
// if there's a pending marker from the entropy stream, return that
// otherwise, fetch from the stream and get a marker. if there's no
// marker, return 0xff, which is never a valid marker value
static uint8 get_marker(jpeg *j)
{
    uint8 x;
    if (j->marker != MARKER_none) { x = j->marker; j->marker = MARKER_none; return x; }
    x = get8u(&j->s);
    if (x != 0xff) return MARKER_none;
    while (x == 0xff)
        x = get8u(&j->s);
    return x;
}

// in each scan, we'll have scan_n components, and the order
// of the components is specified by order[]
#define RESTART(x)     ((x) >= 0xd0 && (x) <= 0xd7)

// after a restart interval, reset the entropy decoder and
// the dc prediction
static void reset(jpeg *j)
{
    j->code_bits = 0;
    j->code_buffer = 0;
    j->nomore = 0;
    j->img_comp[0].dc_pred = j->img_comp[1].dc_pred = j->img_comp[2].dc_pred = 0;
    j->marker = MARKER_none;
    j->todo = j->restart_interval ? j->restart_interval : 0x7fffffff;
    // no more than 1<<31 MCUs if no restart_interal? that's plenty safe,
    // since we don't even allow 1<<30 pixels
}

static int parse_entropy_coded_data(jpeg *z)
{
    reset(z);
    if (z->scan_n == 1) {
        int i,j;
#if STBI_SIMD
        __declspec(align(16))
#endif
        short data[64];
        int n = z->order[0];
        // non-interleaved data, we just need to process one block at a time,
        // in trivial scanline order
        // number of blocks to do just depends on how many actual "pixels" this
        // component has, independent of interleaved MCU blocking and such
        int w = (z->img_comp[n].x+7) >> 3;
        int h = (z->img_comp[n].y+7) >> 3;
        for (j=0; j < h; ++j) {
            for (i=0; i < w; ++i) {
                if (!decode_block(z, data, z->huff_dc+z->img_comp[n].hd, z->huff_ac+z->img_comp[n].ha, n)) return 0;
#if STBI_SIMD
                stbi_idct_installed(z->img_comp[n].data+z->img_comp[n].w2*j*8+i*8, z->img_comp[n].w2, data, z->dequant2[z->img_comp[n].tq]);
#else
                idct_block(z->img_comp[n].data+z->img_comp[n].w2*j*8+i*8, z->img_comp[n].w2, data, z->dequant[z->img_comp[n].tq]);
#endif
                // every data block is an MCU, so countdown the restart interval
                if (--z->todo <= 0) {
                    if (z->code_bits < 24) grow_buffer_unsafe(z);
                    // if it's NOT a restart, then just bail, so we get corrupt data
                    // rather than no data
                    if (!RESTART(z->marker)) return 1;
                    reset(z);
                }
            }
        }
    } else { // interleaved!
        int i,j,k,x,y;
        short data[64];
        for (j=0; j < z->img_mcu_y; ++j) {
            for (i=0; i < z->img_mcu_x; ++i) {
                // scan an interleaved mcu... process scan_n components in order
                for (k=0; k < z->scan_n; ++k) {
                    int n = z->order[k];
                    // scan out an mcu's worth of this component; that's just determined
                    // by the basic H and V specified for the component
                    for (y=0; y < z->img_comp[n].v; ++y) {
                        for (x=0; x < z->img_comp[n].h; ++x) {
                            int x2 = (i*z->img_comp[n].h + x)*8;
                            int y2 = (j*z->img_comp[n].v + y)*8;
                            if (!decode_block(z, data, z->huff_dc+z->img_comp[n].hd, z->huff_ac+z->img_comp[n].ha, n)) return 0;
#if STBI_SIMD
                            stbi_idct_installed(z->img_comp[n].data+z->img_comp[n].w2*y2+x2, z->img_comp[n].w2, data, z->dequant2[z->img_comp[n].tq]);
#else
                            idct_block(z->img_comp[n].data+z->img_comp[n].w2*y2+x2, z->img_comp[n].w2, data, z->dequant[z->img_comp[n].tq]);
#endif
                        }
                    }
                }
                // after all interleaved components, that's an interleaved MCU,
                // so now count down the restart interval
                if (--z->todo <= 0) {
                    if (z->code_bits < 24) grow_buffer_unsafe(z);
                    // if it's NOT a restart, then just bail, so we get corrupt data
                    // rather than no data
                    if (!RESTART(z->marker)) return 1;
                    reset(z);
                }
            }
        }
    }
    return 1;
}

static int process_marker(jpeg *z, int m)
{
    int L;
    switch (m) {
        case MARKER_none: // no marker found
            return e("expected marker","Corrupt JPEG");

        case 0xC2: // SOF - progressive
            return e("progressive jpeg","JPEG format not supported (progressive)");

        case 0xDD: // DRI - specify restart interval
            if (get16(&z->s) != 4) return e("bad DRI len","Corrupt JPEG");
            z->restart_interval = get16(&z->s);
            return 1;

        case 0xDB: // DQT - define quantization table
            L = get16(&z->s)-2;
            while (L > 0) {
                int q = get8(&z->s);
                int p = q >> 4;
                int t = q & 15,i;
                if (p != 0) return e("bad DQT type","Corrupt JPEG");
                if (t > 3) return e("bad DQT table","Corrupt JPEG");
                for (i=0; i < 64; ++i)
                    z->dequant[t][dezigzag[i]] = get8u(&z->s);
#if STBI_SIMD
                for (i=0; i < 64; ++i)
               z->dequant2[t][i] = z->dequant[t][i];
#endif
                L -= 65;
            }
            return L==0;

        case 0xC4: // DHT - define huffman table
            L = get16(&z->s)-2;
            while (L > 0) {
                uint8 *v;
                int sizes[16],i,m=0;
                int q = get8(&z->s);
                int tc = q >> 4;
                int th = q & 15;
                if (tc > 1 || th > 3) return e("bad DHT header","Corrupt JPEG");
                for (i=0; i < 16; ++i) {
                    sizes[i] = get8(&z->s);
                    m += sizes[i];
                }
                L -= 17;
                if (tc == 0) {
                    if (!build_huffman(z->huff_dc+th, sizes)) return 0;
                    v = z->huff_dc[th].values;
                } else {
                    if (!build_huffman(z->huff_ac+th, sizes)) return 0;
                    v = z->huff_ac[th].values;
                }
                for (i=0; i < m; ++i)
                    v[i] = get8u(&z->s);
                L -= m;
            }
            return L==0;
    }
    // check for comment block or APP blocks
    if ((m >= 0xE0 && m <= 0xEF) || m == 0xFE) {
        skip(&z->s, get16(&z->s)-2);
        return 1;
    }
    return 0;
}

// after we see SOS
static int process_scan_header(jpeg *z)
{
    int i;
    int Ls = get16(&z->s);
    z->scan_n = get8(&z->s);
    if (z->scan_n < 1 || z->scan_n > 4 || z->scan_n > (int) z->s.img_n) return e("bad SOS component count","Corrupt JPEG");
    if (Ls != 6+2*z->scan_n) return e("bad SOS len","Corrupt JPEG");
    for (i=0; i < z->scan_n; ++i) {
        int id = get8(&z->s), which;
        int q = get8(&z->s);
        for (which = 0; which < z->s.img_n; ++which)
            if (z->img_comp[which].id == id)
                break;
        if (which == z->s.img_n) return 0;
        z->img_comp[which].hd = q >> 4;   if (z->img_comp[which].hd > 3) return e("bad DC huff","Corrupt JPEG");
        z->img_comp[which].ha = q & 15;   if (z->img_comp[which].ha > 3) return e("bad AC huff","Corrupt JPEG");
        z->order[i] = which;
    }
    if (get8(&z->s) != 0) return e("bad SOS","Corrupt JPEG");
    get8(&z->s); // should be 63, but might be 0
    if (get8(&z->s) != 0) return e("bad SOS","Corrupt JPEG");

    return 1;
}

static int process_frame_header(jpeg *z, int scan)
{
    stbi *s = &z->s;
    int Lf,p,i,q, h_max=1,v_max=1,c;
    Lf = get16(s);         if (Lf < 11) return e("bad SOF len","Corrupt JPEG"); // JPEG
    p  = get8(s);          if (p != 8) return e("only 8-bit","JPEG format not supported: 8-bit only"); // JPEG baseline
    s->img_y = get16(s);   if (s->img_y == 0) return e("no header height", "JPEG format not supported: delayed height"); // Legal, but we don't handle it--but neither does IJG
    s->img_x = get16(s);   if (s->img_x == 0) return e("0 width","Corrupt JPEG"); // JPEG requires
    c = get8(s);
    if (c != 3 && c != 1) return e("bad component count","Corrupt JPEG");    // JFIF requires
    s->img_n = c;
    for (i=0; i < c; ++i) {
        z->img_comp[i].data = NULL;
        z->img_comp[i].linebuf = NULL;
    }

    if (Lf != 8+3*s->img_n) return e("bad SOF len","Corrupt JPEG");

    for (i=0; i < s->img_n; ++i) {
        z->img_comp[i].id = get8(s);
        if (z->img_comp[i].id != i+1)   // JFIF requires
            if (z->img_comp[i].id != i)  // some version of jpegtran outputs non-JFIF-compliant files!
                return e("bad component ID","Corrupt JPEG");
        q = get8(s);
        z->img_comp[i].h = (q >> 4);  if (!z->img_comp[i].h || z->img_comp[i].h > 4) return e("bad H","Corrupt JPEG");
        z->img_comp[i].v = q & 15;    if (!z->img_comp[i].v || z->img_comp[i].v > 4) return e("bad V","Corrupt JPEG");
        z->img_comp[i].tq = get8(s);  if (z->img_comp[i].tq > 3) return e("bad TQ","Corrupt JPEG");
    }

    if (scan != SCAN_load) return 1;

    if ((1 << 30) / s->img_x / s->img_n < s->img_y) return e("too large", "Image too large to decode");

    for (i=0; i < s->img_n; ++i) {
        if (z->img_comp[i].h > h_max) h_max = z->img_comp[i].h;
        if (z->img_comp[i].v > v_max) v_max = z->img_comp[i].v;
    }

    // compute interleaved mcu info
    z->img_h_max = h_max;
    z->img_v_max = v_max;
    z->img_mcu_w = h_max * 8;
    z->img_mcu_h = v_max * 8;
    z->img_mcu_x = (s->img_x + z->img_mcu_w-1) / z->img_mcu_w;
    z->img_mcu_y = (s->img_y + z->img_mcu_h-1) / z->img_mcu_h;

    for (i=0; i < s->img_n; ++i) {
        // number of effective pixels (e.g. for non-interleaved MCU)
        z->img_comp[i].x = (s->img_x * z->img_comp[i].h + h_max-1) / h_max;
        z->img_comp[i].y = (s->img_y * z->img_comp[i].v + v_max-1) / v_max;
        // to simplify generation, we'll allocate enough memory to decode
        // the bogus oversized data from using interleaved MCUs and their
        // big blocks (e.g. a 16x16 iMCU on an image of width 33); we won't
        // discard the extra data until colorspace conversion
        z->img_comp[i].w2 = z->img_mcu_x * z->img_comp[i].h * 8;
        z->img_comp[i].h2 = z->img_mcu_y * z->img_comp[i].v * 8;
        z->img_comp[i].raw_data = malloc(z->img_comp[i].w2 * z->img_comp[i].h2+15);
        if (z->img_comp[i].raw_data == NULL) {
            for(--i; i >= 0; --i) {
                free(z->img_comp[i].raw_data);
                z->img_comp[i].data = NULL;
            }
            return e("outofmem", "Out of memory");
        }
        // align blocks for installable-idct using mmx/sse
        z->img_comp[i].data = (uint8*) (((size_t) z->img_comp[i].raw_data + 15) & ~15);
        z->img_comp[i].linebuf = NULL;
    }

    return 1;
}

// use comparisons since in some cases we handle more than one case (e.g. SOF)
#define DNL(x)         ((x) == 0xdc)
#define SOI(x)         ((x) == 0xd8)
#define EOI(x)         ((x) == 0xd9)
#define SOF(x)         ((x) == 0xc0 || (x) == 0xc1)
#define SOS(x)         ((x) == 0xda)

static int decode_jpeg_header(jpeg *z, int scan)
{
    int m;
    z->marker = MARKER_none; // initialize cached marker to empty
    m = get_marker(z);
    if (!SOI(m)) return e("no SOI","Corrupt JPEG");
    if (scan == SCAN_type) return 1;
    m = get_marker(z);
    while (!SOF(m)) {
        if (!process_marker(z,m)) return 0;
        m = get_marker(z);
        while (m == MARKER_none) {
            // some files have extra padding after their blocks, so ok, we'll scan
            if (at_eof(&z->s)) return e("no SOF", "Corrupt JPEG");
            m = get_marker(z);
        }
    }
    if (!process_frame_header(z, scan)) return 0;
    return 1;
}

static int decode_jpeg_image(jpeg *j)
{
    int m;
    j->restart_interval = 0;
    if (!decode_jpeg_header(j, SCAN_load)) return 0;
    m = get_marker(j);
    while (!EOI(m)) {
        if (SOS(m)) {
            if (!process_scan_header(j)) return 0;
            if (!parse_entropy_coded_data(j)) return 0;
        } else {
            if (!process_marker(j, m)) return 0;
        }
        m = get_marker(j);
    }
    return 1;
}

// static jfif-centered resampling (across block boundaries)

typedef uint8 *(*resample_row_func)(uint8 *out, uint8 *in0, uint8 *in1,
                                    int w, int hs);

#define div4(x) ((uint8) ((x) >> 2))

static uint8 *resample_row_1(uint8 *out, uint8 *in_near, uint8 *in_far, int w, int hs)
{
    return in_near;
}

static uint8* resample_row_v_2(uint8 *out, uint8 *in_near, uint8 *in_far, int w, int hs)
{
    // need to generate two samples vertically for every one in input
    int i;
    for (i=0; i < w; ++i)
        out[i] = div4(3*in_near[i] + in_far[i] + 2);
    return out;
}

static uint8*  resample_row_h_2(uint8 *out, uint8 *in_near, uint8 *in_far, int w, int hs)
{
    // need to generate two samples horizontally for every one in input
    int i;
    uint8 *input = in_near;
    if (w == 1) {
        // if only one sample, can't do any interpolation
        out[0] = out[1] = input[0];
        return out;
    }

    out[0] = input[0];
    out[1] = div4(input[0]*3 + input[1] + 2);
    for (i=1; i < w-1; ++i) {
        int n = 3*input[i]+2;
        out[i*2+0] = div4(n+input[i-1]);
        out[i*2+1] = div4(n+input[i+1]);
    }
    out[i*2+0] = div4(input[w-2]*3 + input[w-1] + 2);
    out[i*2+1] = input[w-1];
    return out;
}

#define div16(x) ((uint8) ((x) >> 4))

static uint8 *resample_row_hv_2(uint8 *out, uint8 *in_near, uint8 *in_far, int w, int hs)
{
    // need to generate 2x2 samples for every one in input
    int i,t0,t1;
    if (w == 1) {
        out[0] = out[1] = div4(3*in_near[0] + in_far[0] + 2);
        return out;
    }

    t1 = 3*in_near[0] + in_far[0];
    out[0] = div4(t1+2);
    for (i=1; i < w; ++i) {
        t0 = t1;
        t1 = 3*in_near[i]+in_far[i];
        out[i*2-1] = div16(3*t0 + t1 + 8);
        out[i*2  ] = div16(3*t1 + t0 + 8);
    }
    out[w*2-1] = div4(t1+2);
    return out;
}

static uint8 *resample_row_generic(uint8 *out, uint8 *in_near, uint8 *in_far, int w, int hs)
{
    // resample with nearest-neighbor
    int i,j;
    for (i=0; i < w; ++i)
        for (j=0; j < hs; ++j)
            out[i*hs+j] = in_near[i];
    return out;
}

#define float2fixed(x)  ((int) ((x) * 65536 + 0.5))

// 0.38 seconds on 3*anemones.jpg   (0.25 with processor = Pro)
// VC6 without processor=Pro is generating multiple LEAs per multiply!
static void YCbCr_to_RGB_row(uint8 *out, const uint8 *y, const uint8 *pcb, const uint8 *pcr, int count, int step)
{
    int i;
    for (i=0; i < count; ++i) {
        int y_fixed = (y[i] << 16) + 32768; // rounding
        int r,g,b;
        int cr = pcr[i] - 128;
        int cb = pcb[i] - 128;
        r = y_fixed + cr*float2fixed(1.40200f);
        g = y_fixed - cr*float2fixed(0.71414f) - cb*float2fixed(0.34414f);
        b = y_fixed                            + cb*float2fixed(1.77200f);
        r >>= 16;
        g >>= 16;
        b >>= 16;
        if ((unsigned) r > 255) { if (r < 0) r = 0; else r = 255; }
        if ((unsigned) g > 255) { if (g < 0) g = 0; else g = 255; }
        if ((unsigned) b > 255) { if (b < 0) b = 0; else b = 255; }
        out[0] = (uint8)r;
        out[1] = (uint8)g;
        out[2] = (uint8)b;
        out[3] = 255;
        out += step;
    }
}

#if STBI_SIMD
static stbi_YCbCr_to_RGB_run stbi_YCbCr_installed = YCbCr_to_RGB_row;

void stbi_install_YCbCr_to_RGB(stbi_YCbCr_to_RGB_run func)
{
   stbi_YCbCr_installed = func;
}
#endif


// clean up the temporary component buffers
static void cleanup_jpeg(jpeg *j)
{
    int i;
    for (i=0; i < j->s.img_n; ++i) {
        if (j->img_comp[i].data) {
            free(j->img_comp[i].raw_data);
            j->img_comp[i].data = NULL;
        }
        if (j->img_comp[i].linebuf) {
            free(j->img_comp[i].linebuf);
            j->img_comp[i].linebuf = NULL;
        }
    }
}

typedef struct
{
    resample_row_func resample;
    uint8 *line0,*line1;
    int hs,vs;   // expansion factor in each axis
    int w_lores; // horizontal pixels pre-expansion
    int ystep;   // how far through vertical expansion we are
    int ypos;    // which pre-expansion row we're on
} stbi_resample;

static uint8 *load_jpeg_image(jpeg *z, int *out_x, int *out_y, int *comp, int req_comp)
{
    int n, decode_n;
    // validate req_comp
    if (req_comp < 0 || req_comp > 4) return epuc("bad req_comp", "Internal error");
    z->s.img_n = 0;

    // load a jpeg image from whichever source
    if (!decode_jpeg_image(z)) { cleanup_jpeg(z); return NULL; }

    // determine actual number of components to generate
    n = req_comp ? req_comp : z->s.img_n;

    if (z->s.img_n == 3 && n < 3)
        decode_n = 1;
    else
        decode_n = z->s.img_n;

    // resample and color-convert
    {
        int k;
        uint i,j;
        uint8 *output;
        uint8 *coutput[4];

        stbi_resample res_comp[4];

        for (k=0; k < decode_n; ++k) {
            stbi_resample *r = &res_comp[k];

            // allocate line buffer big enough for upsampling off the edges
            // with upsample factor of 4
            z->img_comp[k].linebuf = (uint8 *) malloc(z->s.img_x + 3);
            if (!z->img_comp[k].linebuf) { cleanup_jpeg(z); return epuc("outofmem", "Out of memory"); }

            r->hs      = z->img_h_max / z->img_comp[k].h;
            r->vs      = z->img_v_max / z->img_comp[k].v;
            r->ystep   = r->vs >> 1;
            r->w_lores = (z->s.img_x + r->hs-1) / r->hs;
            r->ypos    = 0;
            r->line0   = r->line1 = z->img_comp[k].data;

            if      (r->hs == 1 && r->vs == 1) r->resample = resample_row_1;
            else if (r->hs == 1 && r->vs == 2) r->resample = resample_row_v_2;
            else if (r->hs == 2 && r->vs == 1) r->resample = resample_row_h_2;
            else if (r->hs == 2 && r->vs == 2) r->resample = resample_row_hv_2;
            else                               r->resample = resample_row_generic;
        }

        // can't error after this so, this is safe
        output = (uint8 *) malloc(n * z->s.img_x * z->s.img_y + 1);
        if (!output) { cleanup_jpeg(z); return epuc("outofmem", "Out of memory"); }

        // now go ahead and resample
        for (j=0; j < z->s.img_y; ++j) {
            uint8 *out = output + n * z->s.img_x * j;
            for (k=0; k < decode_n; ++k) {
                stbi_resample *r = &res_comp[k];
                int y_bot = r->ystep >= (r->vs >> 1);
                coutput[k] = r->resample(z->img_comp[k].linebuf,
                                         y_bot ? r->line1 : r->line0,
                                         y_bot ? r->line0 : r->line1,
                                         r->w_lores, r->hs);
                if (++r->ystep >= r->vs) {
                    r->ystep = 0;
                    r->line0 = r->line1;
                    if (++r->ypos < z->img_comp[k].y)
                        r->line1 += z->img_comp[k].w2;
                }
            }
            if (n >= 3) {
                uint8 *y = coutput[0];
                if (z->s.img_n == 3) {
#if STBI_SIMD
                    stbi_YCbCr_installed(out, y, coutput[1], coutput[2], z->s.img_x, n);
#else
                    YCbCr_to_RGB_row(out, y, coutput[1], coutput[2], z->s.img_x, n);
#endif
                } else
                    for (i=0; i < z->s.img_x; ++i) {
                        out[0] = out[1] = out[2] = y[i];
                        out[3] = 255; // not used if n==3
                        out += n;
                    }
            } else {
                uint8 *y = coutput[0];
                if (n == 1)
                    for (i=0; i < z->s.img_x; ++i) out[i] = y[i];
                else
                    for (i=0; i < z->s.img_x; ++i) *out++ = y[i], *out++ = 255;
            }
        }
        cleanup_jpeg(z);
        *out_x = z->s.img_x;
        *out_y = z->s.img_y;
        if (comp) *comp  = z->s.img_n; // report original components, not output
        return output;
    }
}

#ifndef STBI_NO_STDIO
unsigned char *stbi_jpeg_load_from_file(FILE *f, int *x, int *y, int *comp, int req_comp)
{
    jpeg j;
    start_file(&j.s, f);
    return load_jpeg_image(&j, x,y,comp,req_comp);
}

unsigned char *stbi_jpeg_load(char const *filename, int *x, int *y, int *comp, int req_comp)
{
    unsigned char *data;
    FILE *f = fopen(filename, "rb");
    if (!f) return NULL;
    data = stbi_jpeg_load_from_file(f,x,y,comp,req_comp);
    fclose(f);
    return data;
}
#endif

unsigned char *stbi_jpeg_load_from_memory(stbi_uc const *buffer, int len, int *x, int *y, int *comp, int req_comp)
{
    jpeg j;
    start_mem(&j.s, buffer,len);
    return load_jpeg_image(&j, x,y,comp,req_comp);
}

#ifndef STBI_NO_STDIO
int stbi_jpeg_test_file(FILE *f)
{
    int n,r;
    jpeg j;
    n = ftell(f);
    start_file(&j.s, f);
    r = decode_jpeg_header(&j, SCAN_type);
    fseek(f,n,SEEK_SET);
    return r;
}
#endif

int stbi_jpeg_test_memory(stbi_uc const *buffer, int len)
{
    jpeg j;
    start_mem(&j.s, buffer,len);
    return decode_jpeg_header(&j, SCAN_type);
}

// @TODO:
#ifndef STBI_NO_STDIO
extern int      stbi_jpeg_info            (char const *filename,           int *x, int *y, int *comp);
extern int      stbi_jpeg_info_from_file  (FILE *f,                  int *x, int *y, int *comp);
#endif
extern int      stbi_jpeg_info_from_memory(stbi_uc const *buffer, int len, int *x, int *y, int *comp);

// public domain zlib decode    v0.2  Sean Barrett 2006-11-18
//    simple implementation
//      - all input must be provided in an upfront buffer
//      - all output is written to a single output buffer (can malloc/realloc)
//    performance
//      - fast huffman

// fast-way is faster to check than jpeg huffman, but slow way is slower
#define ZFAST_BITS  9 // accelerate all cases in default tables
#define ZFAST_MASK  ((1 << ZFAST_BITS) - 1)

// zlib-style huffman encoding
// (jpegs packs from left, zlib from right, so can't share code)
typedef struct
{
    uint16 fast[1 << ZFAST_BITS];
    uint16 firstcode[16];
    int maxcode[17];
    uint16 firstsymbol[16];
    uint8  size[288];
    uint16 value[288];
} zhuffman;

__forceinline static int bitreverse16(int n)
{
    n = ((n & 0xAAAA) >>  1) | ((n & 0x5555) << 1);
    n = ((n & 0xCCCC) >>  2) | ((n & 0x3333) << 2);
    n = ((n & 0xF0F0) >>  4) | ((n & 0x0F0F) << 4);
    n = ((n & 0xFF00) >>  8) | ((n & 0x00FF) << 8);
    return n;
}

__forceinline static int bit_reverse(int v, int bits)
{
    assert(bits <= 16);
    // to bit reverse n bits, reverse 16 and shift
    // e.g. 11 bits, bit reverse and shift away 5
    return bitreverse16(v) >> (16-bits);
}

static int zbuild_huffman(zhuffman *z, uint8 *sizelist, int num)
{
    int i,k=0;
    int code, next_code[16], sizes[17];

    // DEFLATE spec for generating codes
    memset(sizes, 0, sizeof(sizes));
    memset(z->fast, 255, sizeof(z->fast));
    for (i=0; i < num; ++i)
        ++sizes[sizelist[i]];
    sizes[0] = 0;
    for (i=1; i < 16; ++i)
        assert(sizes[i] <= (1 << i));
    code = 0;
    for (i=1; i < 16; ++i) {
        next_code[i] = code;
        z->firstcode[i] = (uint16) code;
        z->firstsymbol[i] = (uint16) k;
        code = (code + sizes[i]);
        if (sizes[i])
            if (code-1 >= (1 << i)) return e("bad codelengths","Corrupt JPEG");
        z->maxcode[i] = code << (16-i); // preshift for inner loop
        code <<= 1;
        k += sizes[i];
    }
    z->maxcode[16] = 0x10000; // sentinel
    for (i=0; i < num; ++i) {
        int s = sizelist[i];
        if (s) {
            int c = next_code[s] - z->firstcode[s] + z->firstsymbol[s];
            z->size[c] = (uint8)s;
            z->value[c] = (uint16)i;
            if (s <= ZFAST_BITS) {
                int k = bit_reverse(next_code[s],s);
                while (k < (1 << ZFAST_BITS)) {
                    z->fast[k] = (uint16) c;
                    k += (1 << s);
                }
            }
            ++next_code[s];
        }
    }
    return 1;
}

// zlib-from-memory implementation for PNG reading
//    because PNG allows splitting the zlib stream arbitrarily,
//    and it's annoying structurally to have PNG call ZLIB call PNG,
//    we require PNG read all the IDATs and combine them into a single
//    memory buffer

typedef struct
{
    uint8 *zbuffer, *zbuffer_end;
    int num_bits;
    uint32 code_buffer;

    char *zout;
    char *zout_start;
    char *zout_end;
    int   z_expandable;

    zhuffman z_length, z_distance;
} zbuf;

__forceinline static int zget8(zbuf *z)
{
    if (z->zbuffer >= z->zbuffer_end) return 0;
    return *z->zbuffer++;
}

static void fill_bits(zbuf *z)
{
    do {
        assert(z->code_buffer < (1U << z->num_bits));
        z->code_buffer |= zget8(z) << z->num_bits;
        z->num_bits += 8;
    } while (z->num_bits <= 24);
}

__forceinline static unsigned int zreceive(zbuf *z, int n)
{
    unsigned int k;
    if (z->num_bits < n) fill_bits(z);
    k = z->code_buffer & ((1 << n) - 1);
    z->code_buffer >>= n;
    z->num_bits -= n;
    return k;
}

__forceinline static int zhuffman_decode(zbuf *a, zhuffman *z)
{
    int b,s,k;
    if (a->num_bits < 16) fill_bits(a);
    b = z->fast[a->code_buffer & ZFAST_MASK];
    if (b < 0xffff) {
        s = z->size[b];
        a->code_buffer >>= s;
        a->num_bits -= s;
        return z->value[b];
    }

    // not resolved by fast table, so compute it the slow way
    // use jpeg approach, which requires MSbits at top
    k = bit_reverse(a->code_buffer, 16);
    for (s=ZFAST_BITS+1; ; ++s)
        if (k < z->maxcode[s])
            break;
    if (s == 16) return -1; // invalid code!
    // code size is s, so:
    b = (k >> (16-s)) - z->firstcode[s] + z->firstsymbol[s];
    assert(z->size[b] == s);
    a->code_buffer >>= s;
    a->num_bits -= s;
    return z->value[b];
}

static int expand(zbuf *z, int n)  // need to make room for n bytes
{
    char *q;
    int cur, limit;
    if (!z->z_expandable) return e("output buffer limit","Corrupt PNG");
    cur   = (int) (z->zout     - z->zout_start);
    limit = (int) (z->zout_end - z->zout_start);
    while (cur + n > limit)
        limit *= 2;
    q = (char *) realloc(z->zout_start, limit);
    if (q == NULL) return e("outofmem", "Out of memory");
    z->zout_start = q;
    z->zout       = q + cur;
    z->zout_end   = q + limit;
    return 1;
}

static int length_base[31] = {
        3,4,5,6,7,8,9,10,11,13,
        15,17,19,23,27,31,35,43,51,59,
        67,83,99,115,131,163,195,227,258,0,0 };

static int length_extra[31]=
        { 0,0,0,0,0,0,0,0,1,1,1,1,2,2,2,2,3,3,3,3,4,4,4,4,5,5,5,5,0,0,0 };

static int dist_base[32] = { 1,2,3,4,5,7,9,13,17,25,33,49,65,97,129,193,
                             257,385,513,769,1025,1537,2049,3073,4097,6145,8193,12289,16385,24577,0,0};

static int dist_extra[32] =
        { 0,0,0,0,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,13,13};

static int parse_huffman_block(zbuf *a)
{
    for(;;) {
        int z = zhuffman_decode(a, &a->z_length);
        if (z < 256) {
            if (z < 0) return e("bad huffman code","Corrupt PNG"); // error in huffman codes
            if (a->zout >= a->zout_end) if (!expand(a, 1)) return 0;
            *a->zout++ = (char) z;
        } else {
            uint8 *p;
            int len,dist;
            if (z == 256) return 1;
            z -= 257;
            len = length_base[z];
            if (length_extra[z]) len += zreceive(a, length_extra[z]);
            z = zhuffman_decode(a, &a->z_distance);
            if (z < 0) return e("bad huffman code","Corrupt PNG");
            dist = dist_base[z];
            if (dist_extra[z]) dist += zreceive(a, dist_extra[z]);
            if (a->zout - a->zout_start < dist) return e("bad dist","Corrupt PNG");
            if (a->zout + len > a->zout_end) if (!expand(a, len)) return 0;
            p = (uint8 *) (a->zout - dist);
            while (len--)
                *a->zout++ = *p++;
        }
    }
}

static int compute_huffman_codes(zbuf *a)
{
    static uint8 length_dezigzag[19] = { 16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15 };
    zhuffman z_codelength;
    uint8 lencodes[286+32+137];//padding for maximum single op
    uint8 codelength_sizes[19];
    int i,n;

    int hlit  = zreceive(a,5) + 257;
    int hdist = zreceive(a,5) + 1;
    int hclen = zreceive(a,4) + 4;

    memset(codelength_sizes, 0, sizeof(codelength_sizes));
    for (i=0; i < hclen; ++i) {
        int s = zreceive(a,3);
        codelength_sizes[length_dezigzag[i]] = (uint8) s;
    }
    if (!zbuild_huffman(&z_codelength, codelength_sizes, 19)) return 0;

    n = 0;
    while (n < hlit + hdist) {
        int c = zhuffman_decode(a, &z_codelength);
        assert(c >= 0 && c < 19);
        if (c < 16)
            lencodes[n++] = (uint8) c;
        else if (c == 16) {
            c = zreceive(a,2)+3;
            memset(lencodes+n, lencodes[n-1], c);
            n += c;
        } else if (c == 17) {
            c = zreceive(a,3)+3;
            memset(lencodes+n, 0, c);
            n += c;
        } else {
            assert(c == 18);
            c = zreceive(a,7)+11;
            memset(lencodes+n, 0, c);
            n += c;
        }
    }
    if (n != hlit+hdist) return e("bad codelengths","Corrupt PNG");
    if (!zbuild_huffman(&a->z_length, lencodes, hlit)) return 0;
    if (!zbuild_huffman(&a->z_distance, lencodes+hlit, hdist)) return 0;
    return 1;
}

static int parse_uncompressed_block(zbuf *a)
{
    uint8 header[4];
    int len,nlen,k;
    if (a->num_bits & 7)
        zreceive(a, a->num_bits & 7); // discard
    // drain the bit-packed data into header
    k = 0;
    while (a->num_bits > 0) {
        header[k++] = (uint8) (a->code_buffer & 255); // wtf this warns?
        a->code_buffer >>= 8;
        a->num_bits -= 8;
    }
    assert(a->num_bits == 0);
    // now fill header the normal way
    while (k < 4)
        header[k++] = (uint8) zget8(a);
    len  = header[1] * 256 + header[0];
    nlen = header[3] * 256 + header[2];
    if (nlen != (len ^ 0xffff)) return e("zlib corrupt","Corrupt PNG");
    if (a->zbuffer + len > a->zbuffer_end) return e("read past buffer","Corrupt PNG");
    if (a->zout + len > a->zout_end)
        if (!expand(a, len)) return 0;
    memcpy(a->zout, a->zbuffer, len);
    a->zbuffer += len;
    a->zout += len;
    return 1;
}

static int parse_zlib_header(zbuf *a)
{
    int cmf   = zget8(a);
    int cm    = cmf & 15;
    /* int cinfo = cmf >> 4; */
    int flg   = zget8(a);
    if ((cmf*256+flg) % 31 != 0) return e("bad zlib header","Corrupt PNG"); // zlib spec
    if (flg & 32) return e("no preset dict","Corrupt PNG"); // preset dictionary not allowed in png
    if (cm != 8) return e("bad compression","Corrupt PNG"); // DEFLATE required for png
    // window = 1 << (8 + cinfo)... but who cares, we fully buffer output
    return 1;
}

// @TODO: should statically initialize these for optimal thread safety
static uint8 default_length[288], default_distance[32];
static void init_defaults(void)
{
    int i;   // use <= to match clearly with spec
    for (i=0; i <= 143; ++i)     default_length[i]   = 8;
    for (   ; i <= 255; ++i)     default_length[i]   = 9;
    for (   ; i <= 279; ++i)     default_length[i]   = 7;
    for (   ; i <= 287; ++i)     default_length[i]   = 8;

    for (i=0; i <=  31; ++i)     default_distance[i] = 5;
}

int stbi_png_partial; // a quick hack to only allow decoding some of a PNG... I should implement real streaming support instead
static int parse_zlib(zbuf *a, int parse_header)
{
    int final, type;
    if (parse_header)
        if (!parse_zlib_header(a)) return 0;
    a->num_bits = 0;
    a->code_buffer = 0;
    do {
        final = zreceive(a,1);
        type = zreceive(a,2);
        if (type == 0) {
            if (!parse_uncompressed_block(a)) return 0;
        } else if (type == 3) {
            return 0;
        } else {
            if (type == 1) {
                // use fixed code lengths
                if (!default_distance[31]) init_defaults();
                if (!zbuild_huffman(&a->z_length  , default_length  , 288)) return 0;
                if (!zbuild_huffman(&a->z_distance, default_distance,  32)) return 0;
            } else {
                if (!compute_huffman_codes(a)) return 0;
            }
            if (!parse_huffman_block(a)) return 0;
        }
        if (stbi_png_partial && a->zout - a->zout_start > 65536)
            break;
    } while (!final);
    return 1;
}

static int do_zlib(zbuf *a, char *obuf, int olen, int exp, int parse_header)
{
    a->zout_start = obuf;
    a->zout       = obuf;
    a->zout_end   = obuf + olen;
    a->z_expandable = exp;

    return parse_zlib(a, parse_header);
}

char *stbi_zlib_decode_malloc_guesssize(const char *buffer, int len, int initial_size, int *outlen)
{
    zbuf a;
    char *p = (char *) malloc(initial_size);
    if (p == NULL) return NULL;
    a.zbuffer = (uint8 *) buffer;
    a.zbuffer_end = (uint8 *) buffer + len;
    if (do_zlib(&a, p, initial_size, 1, 1)) {
        if (outlen) *outlen = (int) (a.zout - a.zout_start);
        return a.zout_start;
    } else {
        free(a.zout_start);
        return NULL;
    }
}

char *stbi_zlib_decode_malloc(char const *buffer, int len, int *outlen)
{
    return stbi_zlib_decode_malloc_guesssize(buffer, len, 16384, outlen);
}

int stbi_zlib_decode_buffer(char *obuffer, int olen, char const *ibuffer, int ilen)
{
    zbuf a;
    a.zbuffer = (uint8 *) ibuffer;
    a.zbuffer_end = (uint8 *) ibuffer + ilen;
    if (do_zlib(&a, obuffer, olen, 0, 1))
        return (int) (a.zout - a.zout_start);
    else
        return -1;
}

char *stbi_zlib_decode_noheader_malloc(char const *buffer, int len, int *outlen)
{
    zbuf a;
    char *p = (char *) malloc(16384);
    if (p == NULL) return NULL;
    a.zbuffer = (uint8 *) buffer;
    a.zbuffer_end = (uint8 *) buffer+len;
    if (do_zlib(&a, p, 16384, 1, 0)) {
        if (outlen) *outlen = (int) (a.zout - a.zout_start);
        return a.zout_start;
    } else {
        free(a.zout_start);
        return NULL;
    }
}

int stbi_zlib_decode_noheader_buffer(char *obuffer, int olen, const char *ibuffer, int ilen)
{
    zbuf a;
    a.zbuffer = (uint8 *) ibuffer;
    a.zbuffer_end = (uint8 *) ibuffer + ilen;
    if (do_zlib(&a, obuffer, olen, 0, 0))
        return (int) (a.zout - a.zout_start);
    else
        return -1;
}

// public domain "baseline" PNG decoder   v0.10  Sean Barrett 2006-11-18
//    simple implementation
//      - only 8-bit samples
//      - no CRC checking
//      - allocates lots of intermediate memory
//        - avoids problem of streaming data between subsystems
//        - avoids explicit window management
//    performance
//      - uses stb_zlib, a PD zlib implementation with fast huffman decoding


typedef struct
{
    uint32 length;
    uint32 type;
} chunk;

#define PNG_TYPE(a,b,c,d)  (((a) << 24) + ((b) << 16) + ((c) << 8) + (d))

static chunk get_chunk_header(stbi *s)
{
    chunk c;
    c.length = get32(s);
    c.type   = get32(s);
    return c;
}

static int check_png_header(stbi *s)
{
    static uint8 png_sig[8] = { 137,80,78,71,13,10,26,10 };
    int i;
    for (i=0; i < 8; ++i)
        if (get8(s) != png_sig[i]) return e("bad png sig","Not a PNG");
    return 1;
}

typedef struct
{
    stbi s;
    uint8 *idata, *expanded, *out;
} png;


enum {
    F_none=0, F_sub=1, F_up=2, F_avg=3, F_paeth=4,
    F_avg_first, F_paeth_first
};

static uint8 first_row_filter[5] =
        {
                F_none, F_sub, F_none, F_avg_first, F_paeth_first
        };

static int paeth(int a, int b, int c)
{
    int p = a + b - c;
    int pa = abs(p-a);
    int pb = abs(p-b);
    int pc = abs(p-c);
    if (pa <= pb && pa <= pc) return a;
    if (pb <= pc) return b;
    return c;
}

// create the png data from post-deflated data
static int create_png_image_raw(png *a, uint8 *raw, uint32 raw_len, int out_n, uint32 x, uint32 y)
{
    stbi *s = &a->s;
    uint32 i,j,stride = x*out_n;
    int k;
    int img_n = s->img_n; // copy it into a local for later
    assert(out_n == s->img_n || out_n == s->img_n+1);
    if (stbi_png_partial) y = 1;
    a->out = (uint8 *) malloc(x * y * out_n);
    if (!a->out) return e("outofmem", "Out of memory");
    if (!stbi_png_partial) {
        if (s->img_x == x && s->img_y == y) {
            if (raw_len != (img_n * x + 1) * y) return e("not enough pixels","Corrupt PNG");
        } else { // interlaced:
            if (raw_len < (img_n * x + 1) * y) return e("not enough pixels","Corrupt PNG");
        }
    }
    for (j=0; j < y; ++j) {
        uint8 *cur = a->out + stride*j;
        uint8 *prior = cur - stride;
        int filter = *raw++;
        if (filter > 4) return e("invalid filter","Corrupt PNG");
        // if first row, use special filter that doesn't sample previous row
        if (j == 0) filter = first_row_filter[filter];
        // handle first pixel explicitly
        for (k=0; k < img_n; ++k) {
            switch(filter) {
                case F_none       : cur[k] = raw[k]; break;
                case F_sub        : cur[k] = raw[k]; break;
                case F_up         : cur[k] = raw[k] + prior[k]; break;
                case F_avg        : cur[k] = raw[k] + (prior[k]>>1); break;
                case F_paeth      : cur[k] = (uint8) (raw[k] + paeth(0,prior[k],0)); break;
                case F_avg_first  : cur[k] = raw[k]; break;
                case F_paeth_first: cur[k] = raw[k]; break;
            }
        }
        if (img_n != out_n) cur[img_n] = 255;
        raw += img_n;
        cur += out_n;
        prior += out_n;
        // this is a little gross, so that we don't switch per-pixel or per-component
        if (img_n == out_n) {
#define CASE(f) \
             case f:     \
                for (i=x-1; i >= 1; --i, raw+=img_n,cur+=img_n,prior+=img_n) \
                   for (k=0; k < img_n; ++k)
            switch(filter) {
                CASE(F_none)  cur[k] = raw[k]; break;
                CASE(F_sub)   cur[k] = raw[k] + cur[k-img_n]; break;
                CASE(F_up)    cur[k] = raw[k] + prior[k]; break;
                CASE(F_avg)   cur[k] = raw[k] + ((prior[k] + cur[k-img_n])>>1); break;
                CASE(F_paeth)  cur[k] = (uint8) (raw[k] + paeth(cur[k-img_n],prior[k],prior[k-img_n])); break;
                CASE(F_avg_first)    cur[k] = raw[k] + (cur[k-img_n] >> 1); break;
                CASE(F_paeth_first)  cur[k] = (uint8) (raw[k] + paeth(cur[k-img_n],0,0)); break;
            }
#undef CASE
        } else {
            assert(img_n+1 == out_n);
#define CASE(f) \
             case f:     \
                for (i=x-1; i >= 1; --i, cur[img_n]=255,raw+=img_n,cur+=out_n,prior+=out_n) \
                   for (k=0; k < img_n; ++k)
            switch(filter) {
                CASE(F_none)  cur[k] = raw[k]; break;
                CASE(F_sub)   cur[k] = raw[k] + cur[k-out_n]; break;
                CASE(F_up)    cur[k] = raw[k] + prior[k]; break;
                CASE(F_avg)   cur[k] = raw[k] + ((prior[k] + cur[k-out_n])>>1); break;
                CASE(F_paeth)  cur[k] = (uint8) (raw[k] + paeth(cur[k-out_n],prior[k],prior[k-out_n])); break;
                CASE(F_avg_first)    cur[k] = raw[k] + (cur[k-out_n] >> 1); break;
                CASE(F_paeth_first)  cur[k] = (uint8) (raw[k] + paeth(cur[k-out_n],0,0)); break;
            }
#undef CASE
        }
    }
    return 1;
}

static int create_png_image(png *a, uint8 *raw, uint32 raw_len, int out_n, int interlaced)
{
    uint8 *final;
    int p;
    int save;
    if (!interlaced)
        return create_png_image_raw(a, raw, raw_len, out_n, a->s.img_x, a->s.img_y);
    save = stbi_png_partial;
    stbi_png_partial = 0;

    // de-interlacing
    final = (uint8 *) malloc(a->s.img_x * a->s.img_y * out_n);
    for (p=0; p < 7; ++p) {
        int xorig[] = { 0,4,0,2,0,1,0 };
        int yorig[] = { 0,0,4,0,2,0,1 };
        int xspc[]  = { 8,8,4,4,2,2,1 };
        int yspc[]  = { 8,8,8,4,4,2,2 };
        int i,j,x,y;
        // pass1_x[4] = 0, pass1_x[5] = 1, pass1_x[12] = 1
        x = (a->s.img_x - xorig[p] + xspc[p]-1) / xspc[p];
        y = (a->s.img_y - yorig[p] + yspc[p]-1) / yspc[p];
        if (x && y) {
            if (!create_png_image_raw(a, raw, raw_len, out_n, x, y)) {
                free(final);
                return 0;
            }
            for (j=0; j < y; ++j)
                for (i=0; i < x; ++i)
                    memcpy(final + (j*yspc[p]+yorig[p])*a->s.img_x*out_n + (i*xspc[p]+xorig[p])*out_n,
                           a->out + (j*x+i)*out_n, out_n);
            free(a->out);
            raw += (x*out_n+1)*y;
            raw_len -= (x*out_n+1)*y;
        }
    }
    a->out = final;

    stbi_png_partial = save;
    return 1;
}

static int compute_transparency(png *z, uint8 tc[3], int out_n)
{
    stbi *s = &z->s;
    uint32 i, pixel_count = s->img_x * s->img_y;
    uint8 *p = z->out;

    // compute color-based transparency, assuming we've
    // already got 255 as the alpha value in the output
    assert(out_n == 2 || out_n == 4);

    if (out_n == 2) {
        for (i=0; i < pixel_count; ++i) {
            p[1] = (p[0] == tc[0] ? 0 : 255);
            p += 2;
        }
    } else {
        for (i=0; i < pixel_count; ++i) {
            if (p[0] == tc[0] && p[1] == tc[1] && p[2] == tc[2])
                p[3] = 0;
            p += 4;
        }
    }
    return 1;
}

static int expand_palette(png *a, uint8 *palette, int len, int pal_img_n)
{
    uint32 i, pixel_count = a->s.img_x * a->s.img_y;
    uint8 *p, *temp_out, *orig = a->out;

    p = (uint8 *) malloc(pixel_count * pal_img_n);
    if (p == NULL) return e("outofmem", "Out of memory");

    // between here and free(out) below, exitting would leak
    temp_out = p;

    if (pal_img_n == 3) {
        for (i=0; i < pixel_count; ++i) {
            int n = orig[i]*4;
            p[0] = palette[n  ];
            p[1] = palette[n+1];
            p[2] = palette[n+2];
            p += 3;
        }
    } else {
        for (i=0; i < pixel_count; ++i) {
            int n = orig[i]*4;
            p[0] = palette[n  ];
            p[1] = palette[n+1];
            p[2] = palette[n+2];
            p[3] = palette[n+3];
            p += 4;
        }
    }
    free(a->out);
    a->out = temp_out;
    return 1;
}

static int parse_png_file(png *z, int scan, int req_comp)
{
    uint8 palette[1024], pal_img_n=0;
    uint8 has_trans=0, tc[3];
    uint32 ioff=0, idata_limit=0, i, pal_len=0;
    int first=1,k,interlace=0;
    stbi *s = &z->s;

    if (!check_png_header(s)) return 0;

    if (scan == SCAN_type) return 1;

    for(;;first=0) {
        chunk c = get_chunk_header(s);
        if (first && c.type != PNG_TYPE('I','H','D','R'))
            return e("first not IHDR","Corrupt PNG");
        switch (c.type) {
            case PNG_TYPE('I','H','D','R'): {
                int depth,color,comp,filter;
                if (!first) return e("multiple IHDR","Corrupt PNG");
                if (c.length != 13) return e("bad IHDR len","Corrupt PNG");
                s->img_x = get32(s); if (s->img_x > (1 << 24)) return e("too large","Very large image (corrupt?)");
                s->img_y = get32(s); if (s->img_y > (1 << 24)) return e("too large","Very large image (corrupt?)");
                depth = get8(s);  if (depth != 8)        return e("8bit only","PNG not supported: 8-bit only");
                color = get8(s);  if (color > 6)         return e("bad ctype","Corrupt PNG");
                if (color == 3) pal_img_n = 3; else if (color & 1) return e("bad ctype","Corrupt PNG");
                comp  = get8(s);  if (comp) return e("bad comp method","Corrupt PNG");
                filter= get8(s);  if (filter) return e("bad filter method","Corrupt PNG");
                interlace = get8(s); if (interlace>1) return e("bad interlace method","Corrupt PNG");
                if (!s->img_x || !s->img_y) return e("0-pixel image","Corrupt PNG");
                if (!pal_img_n) {
                    s->img_n = (color & 2 ? 3 : 1) + (color & 4 ? 1 : 0);
                    if ((1 << 30) / s->img_x / s->img_n < s->img_y) return e("too large", "Image too large to decode");
                    if (scan == SCAN_header) return 1;
                } else {
                    // if paletted, then pal_n is our final components, and
                    // img_n is # components to decompress/filter.
                    s->img_n = 1;
                    if ((1 << 30) / s->img_x / 4 < s->img_y) return e("too large","Corrupt PNG");
                    // if SCAN_header, have to scan to see if we have a tRNS
                }
                break;
            }

            case PNG_TYPE('P','L','T','E'):  {
                if (c.length > 256*3) return e("invalid PLTE","Corrupt PNG");
                pal_len = c.length / 3;
                if (pal_len * 3 != c.length) return e("invalid PLTE","Corrupt PNG");
                for (i=0; i < pal_len; ++i) {
                    palette[i*4+0] = get8u(s);
                    palette[i*4+1] = get8u(s);
                    palette[i*4+2] = get8u(s);
                    palette[i*4+3] = 255;
                }
                break;
            }

            case PNG_TYPE('t','R','N','S'): {
                if (z->idata) return e("tRNS after IDAT","Corrupt PNG");
                if (pal_img_n) {
                    if (scan == SCAN_header) { s->img_n = 4; return 1; }
                    if (pal_len == 0) return e("tRNS before PLTE","Corrupt PNG");
                    if (c.length > pal_len) return e("bad tRNS len","Corrupt PNG");
                    pal_img_n = 4;
                    for (i=0; i < c.length; ++i)
                        palette[i*4+3] = get8u(s);
                } else {
                    if (!(s->img_n & 1)) return e("tRNS with alpha","Corrupt PNG");
                    if (c.length != (uint32) s->img_n*2) return e("bad tRNS len","Corrupt PNG");
                    has_trans = 1;
                    for (k=0; k < s->img_n; ++k)
                        tc[k] = (uint8) get16(s); // non 8-bit images will be larger
                }
                break;
            }

            case PNG_TYPE('I','D','A','T'): {
                if (pal_img_n && !pal_len) return e("no PLTE","Corrupt PNG");
                if (scan == SCAN_header) { s->img_n = pal_img_n; return 1; }
                if (ioff + c.length > idata_limit) {
                    uint8 *p;
                    if (idata_limit == 0) idata_limit = c.length > 4096 ? c.length : 4096;
                    while (ioff + c.length > idata_limit)
                        idata_limit *= 2;
                    p = (uint8 *) realloc(z->idata, idata_limit); if (p == NULL) return e("outofmem", "Out of memory");
                    z->idata = p;
                }
#ifndef STBI_NO_STDIO
                if (s->img_file)
                {
                    if (fread(z->idata+ioff,1,c.length,s->img_file) != c.length) return e("outofdata","Corrupt PNG");
                }
                else
#endif
                {
                    memcpy(z->idata+ioff, s->img_buffer, c.length);
                    s->img_buffer += c.length;
                }
                ioff += c.length;
                break;
            }

            case PNG_TYPE('I','E','N','D'): {
                uint32 raw_len;
                if (scan != SCAN_load) return 1;
                if (z->idata == NULL) return e("no IDAT","Corrupt PNG");
                z->expanded = (uint8 *) stbi_zlib_decode_malloc((char *) z->idata, ioff, (int *) &raw_len);
                if (z->expanded == NULL) return 0; // zlib should set error
                free(z->idata); z->idata = NULL;
                if ((req_comp == s->img_n+1 && req_comp != 3 && !pal_img_n) || has_trans)
                    s->img_out_n = s->img_n+1;
                else
                    s->img_out_n = s->img_n;
                if (!create_png_image(z, z->expanded, raw_len, s->img_out_n, interlace)) return 0;
                if (has_trans)
                    if (!compute_transparency(z, tc, s->img_out_n)) return 0;
                if (pal_img_n) {
                    // pal_img_n == 3 or 4
                    s->img_n = pal_img_n; // record the actual colors we had
                    s->img_out_n = pal_img_n;
                    if (req_comp >= 3) s->img_out_n = req_comp;
                    if (!expand_palette(z, palette, pal_len, s->img_out_n))
                        return 0;
                }
                free(z->expanded); z->expanded = NULL;
                return 1;
            }

            default:
                // if critical, fail
                if ((c.type & (1 << 29)) == 0) {
#ifndef STBI_NO_FAILURE_STRINGS
                    // not threadsafe
                    static char invalid_chunk[] = "XXXX chunk not known";
                    invalid_chunk[0] = (uint8) (c.type >> 24);
                    invalid_chunk[1] = (uint8) (c.type >> 16);
                    invalid_chunk[2] = (uint8) (c.type >>  8);
                    invalid_chunk[3] = (uint8) (c.type >>  0);
#endif
                    return e(invalid_chunk, "PNG not supported: unknown chunk type");
                }
                skip(s, c.length);
                break;
        }
        // end of chunk, read and skip CRC
        get32(s);
    }
}

static unsigned char *do_png(png *p, int *x, int *y, int *n, int req_comp)
{
    unsigned char *result=NULL;
    p->expanded = NULL;
    p->idata = NULL;
    p->out = NULL;
    if (req_comp < 0 || req_comp > 4) return epuc("bad req_comp", "Internal error");
    if (parse_png_file(p, SCAN_load, req_comp)) {
        result = p->out;
        p->out = NULL;
        if (req_comp && req_comp != p->s.img_out_n) {
            result = convert_format(result, p->s.img_out_n, req_comp, p->s.img_x, p->s.img_y);
            p->s.img_out_n = req_comp;
            if (result == NULL) return result;
        }
        *x = p->s.img_x;
        *y = p->s.img_y;
        if (n) *n = p->s.img_n;
    }
    free(p->out);      p->out      = NULL;
    free(p->expanded); p->expanded = NULL;
    free(p->idata);    p->idata    = NULL;

    return result;
}

#ifndef STBI_NO_STDIO
unsigned char *stbi_png_load_from_file(FILE *f, int *x, int *y, int *comp, int req_comp)
{
    png p;
    start_file(&p.s, f);
    return do_png(&p, x,y,comp,req_comp);
}

unsigned char *stbi_png_load(char const *filename, int *x, int *y, int *comp, int req_comp)
{
    unsigned char *data;
    FILE *f = fopen(filename, "rb");
    if (!f) return NULL;
    data = stbi_png_load_from_file(f,x,y,comp,req_comp);
    fclose(f);
    return data;
}
#endif

unsigned char *stbi_png_load_from_memory(stbi_uc const *buffer, int len, int *x, int *y, int *comp, int req_comp)
{
    png p;
    start_mem(&p.s, buffer,len);
    return do_png(&p, x,y,comp,req_comp);
}

#ifndef STBI_NO_STDIO
int stbi_png_test_file(FILE *f)
{
    png p;
    int n,r;
    n = ftell(f);
    start_file(&p.s, f);
    r = parse_png_file(&p, SCAN_type,STBI_default);
    fseek(f,n,SEEK_SET);
    return r;
}
#endif

int stbi_png_test_memory(stbi_uc const *buffer, int len)
{
    png p;
    start_mem(&p.s, buffer, len);
    return parse_png_file(&p, SCAN_type,STBI_default);
}

// TODO: load header from png
#ifndef STBI_NO_STDIO
int      stbi_png_info             (char const *filename,           int *x, int *y, int *comp)
{
    png p;
    FILE *f = fopen(filename, "rb");
    if (!f) return 0;
    start_file(&p.s, f);
    if (parse_png_file(&p, SCAN_header, 0)) {
        if(x) *x = p.s.img_x;
        if(y) *y = p.s.img_y;
        if (comp) *comp = p.s.img_n;
        fclose(f);
        return 1;
    }
    fclose(f);
    return 0;
}

extern int      stbi_png_info_from_file   (FILE *f,                  int *x, int *y, int *comp);
#endif
extern int      stbi_png_info_from_memory (stbi_uc const *buffer, int len, int *x, int *y, int *comp);

// Microsoft/Windows BMP image

static int bmp_test(stbi *s)
{
    int sz;
    if (get8(s) != 'B') return 0;
    if (get8(s) != 'M') return 0;
    get32le(s); // discard filesize
    get16le(s); // discard reserved
    get16le(s); // discard reserved
    get32le(s); // discard data offset
    sz = get32le(s);
    if (sz == 12 || sz == 40 || sz == 56 || sz == 108) return 1;
    return 0;
}

#ifndef STBI_NO_STDIO
int      stbi_bmp_test_file        (FILE *f)
{
    stbi s;
    int r,n = ftell(f);
    start_file(&s,f);
    r = bmp_test(&s);
    fseek(f,n,SEEK_SET);
    return r;
}
#endif

int      stbi_bmp_test_memory      (stbi_uc const *buffer, int len)
{
    stbi s;
    start_mem(&s, buffer, len);
    return bmp_test(&s);
}

// returns 0..31 for the highest set bit
static int high_bit(unsigned int z)
{
    int n=0;
    if (z == 0) return -1;
    if (z >= 0x10000) n += 16, z >>= 16;
    if (z >= 0x00100) n +=  8, z >>=  8;
    if (z >= 0x00010) n +=  4, z >>=  4;
    if (z >= 0x00004) n +=  2, z >>=  2;
    if (z >= 0x00002) n +=  1, z >>=  1;
    return n;
}

static int bitcount(unsigned int a)
{
    a = (a & 0x55555555) + ((a >>  1) & 0x55555555); // max 2
    a = (a & 0x33333333) + ((a >>  2) & 0x33333333); // max 4
    a = (a + (a >> 4)) & 0x0f0f0f0f; // max 8 per 4, now 8 bits
    a = (a + (a >> 8)); // max 16 per 8 bits
    a = (a + (a >> 16)); // max 32 per 8 bits
    return a & 0xff;
}

static int shiftsigned(int v, int shift, int bits)
{
    int result;
    int z=0;

    if (shift < 0) v <<= -shift;
    else v >>= shift;
    result = v;

    z = bits;
    while (z < 8) {
        result += v >> z;
        z += bits;
    }
    return result;
}

static stbi_uc *bmp_load(stbi *s, int *x, int *y, int *comp, int req_comp)
{
    uint8 *out;
    unsigned int mr=0,mg=0,mb=0,ma=0, fake_a=0;
    stbi_uc pal[256][4];
    int psize=0,i,j,compress=0,width;
    int bpp, flip_vertically, pad, target, offset, hsz;
    if (get8(s) != 'B' || get8(s) != 'M') return epuc("not BMP", "Corrupt BMP");
    get32le(s); // discard filesize
    get16le(s); // discard reserved
    get16le(s); // discard reserved
    offset = get32le(s);
    hsz = get32le(s);
    if (hsz != 12 && hsz != 40 && hsz != 56 && hsz != 108) return epuc("unknown BMP", "BMP type not supported: unknown");
    failure_reason = (char *)"bad BMP";
    if (hsz == 12) {
        s->img_x = get16le(s);
        s->img_y = get16le(s);
    } else {
        s->img_x = get32le(s);
        s->img_y = get32le(s);
    }
    if (get16le(s) != 1) return 0;
    bpp = get16le(s);
    if (bpp == 1) return epuc("monochrome", "BMP type not supported: 1-bit");
    flip_vertically = ((int) s->img_y) > 0;
    s->img_y = abs((int) s->img_y);
    if (hsz == 12) {
        if (bpp < 24)
            psize = (offset - 14 - 24) / 3;
    } else {
        compress = get32le(s);
        if (compress == 1 || compress == 2) return epuc("BMP RLE", "BMP type not supported: RLE");
        get32le(s); // discard sizeof
        get32le(s); // discard hres
        get32le(s); // discard vres
        get32le(s); // discard colorsused
        get32le(s); // discard max important
        if (hsz == 40 || hsz == 56) {
            if (hsz == 56) {
                get32le(s);
                get32le(s);
                get32le(s);
                get32le(s);
            }
            if (bpp == 16 || bpp == 32) {
                mr = mg = mb = 0;
                if (compress == 0) {
                    if (bpp == 32) {
                        mr = 0xffu << 16;
                        mg = 0xffu <<  8;
                        mb = 0xffu <<  0;
                        ma = 0xffu << 24;
                        fake_a = 1; // @TODO: check for cases like alpha value is all 0 and switch it to 255
                    } else {
                        mr = 31 << 10;
                        mg = 31 <<  5;
                        mb = 31 <<  0;
                    }
                } else if (compress == 3) {
                    mr = get32le(s);
                    mg = get32le(s);
                    mb = get32le(s);
                    // not documented, but generated by photoshop and handled by mspaint
                    if (mr == mg && mg == mb) {
                        // ?!?!?
                        return NULL;
                    }
                } else
                    return NULL;
            }
        } else {
            assert(hsz == 108);
            mr = get32le(s);
            mg = get32le(s);
            mb = get32le(s);
            ma = get32le(s);
            get32le(s); // discard color space
            for (i=0; i < 12; ++i)
                get32le(s); // discard color space parameters
        }
        if (bpp < 16)
            psize = (offset - 14 - hsz) >> 2;
    }
    s->img_n = ma ? 4 : 3;
    if (req_comp && req_comp >= 3) // we can directly decode 3 or 4
        target = req_comp;
    else
        target = s->img_n; // if they want monochrome, we'll post-convert
    out = (stbi_uc *) malloc(target * s->img_x * s->img_y);
    if (!out) return epuc("outofmem", "Out of memory");
    if (bpp < 16) {
        int z=0;
        if (psize == 0 || psize > 256) { free(out); return epuc("invalid", "Corrupt BMP"); }
        for (i=0; i < psize; ++i) {
            pal[i][2] = static_cast<stbi_uc>(get8(s));
            pal[i][1] = static_cast<stbi_uc>(get8(s));
            pal[i][0] = static_cast<stbi_uc>(get8(s));
            if (hsz != 12) get8(s);
            pal[i][3] = 255;
        }
        skip(s, offset - 14 - hsz - psize * (hsz == 12 ? 3 : 4));
        if (bpp == 4) width = (s->img_x + 1) >> 1;
        else if (bpp == 8) width = s->img_x;
        else { free(out); return epuc("bad bpp", "Corrupt BMP"); }
        pad = (-width)&3;
        for (j=0; j < (int) s->img_y; ++j) {
            for (i=0; i < (int) s->img_x; i += 2) {
                int v=get8(s),v2=0;
                if (bpp == 4) {
                    v2 = v & 15;
                    v >>= 4;
                }
                out[z++] = pal[v][0];
                out[z++] = pal[v][1];
                out[z++] = pal[v][2];
                if (target == 4) out[z++] = 255;
                if (i+1 == (int) s->img_x) break;
                v = (bpp == 8) ? get8(s) : v2;
                out[z++] = pal[v][0];
                out[z++] = pal[v][1];
                out[z++] = pal[v][2];
                if (target == 4) out[z++] = 255;
            }
            skip(s, pad);
        }
    } else {
        int rshift=0,gshift=0,bshift=0,ashift=0,rcount=0,gcount=0,bcount=0,acount=0;
        int z = 0;
        int easy=0;
        skip(s, offset - 14 - hsz);
        if (bpp == 24) width = 3 * s->img_x;
        else if (bpp == 16) width = 2*s->img_x;
        else /* bpp = 32 and pad = 0 */ width=0;
        pad = (-width) & 3;
        if (bpp == 24) {
            easy = 1;
        } else if (bpp == 32) {
            if (mb == 0xff && mg == 0xff00 && mr == 0xff000000 && ma == 0xff000000)
                easy = 2;
        }
        if (!easy) {
            if (!mr || !mg || !mb) return epuc("bad masks", "Corrupt BMP");
            // right shift amt to put high bit in position #7
            rshift = high_bit(mr)-7; rcount = bitcount(mr);
            gshift = high_bit(mg)-7; gcount = bitcount(mr);
            bshift = high_bit(mb)-7; bcount = bitcount(mr);
            ashift = high_bit(ma)-7; acount = bitcount(mr);
        }
        for (j=0; j < (int) s->img_y; ++j) {
            if (easy) {
                for (i=0; i < (int) s->img_x; ++i) {
                    int a;
                    out[z+2] = static_cast<uint8>(get8(s));
                    out[z+1] = static_cast<uint8>(get8(s));
                    out[z+0] = static_cast<uint8>(get8(s));
                    z += 3;
                    a = (easy == 2 ? get8(s) : 255);
                    if (target == 4) out[z++] = static_cast<uint8>(a);
                }
            } else {
                for (i=0; i < (int) s->img_x; ++i) {
                    uint32 v = (bpp == 16 ? get16le(s) : get32le(s));
                    int a;
                    out[z++] = static_cast<uint8>(shiftsigned(v & mr, rshift, rcount));
                    out[z++] = static_cast<uint8>(shiftsigned(v & mg, gshift, gcount));
                    out[z++] = static_cast<uint8>(shiftsigned(v & mb, bshift, bcount));
                    a = (ma ? shiftsigned(v & ma, ashift, acount) : 255);
                    if (target == 4) out[z++] = static_cast<uint8>(a);
                }
            }
            skip(s, pad);
        }
    }
    if (flip_vertically) {
        stbi_uc t;
        for (j=0; j < (int) s->img_y>>1; ++j) {
            stbi_uc *p1 = out +      j     *s->img_x*target;
            stbi_uc *p2 = out + (s->img_y-1-j)*s->img_x*target;
            for (i=0; i < (int) s->img_x*target; ++i) {
                t = p1[i], p1[i] = p2[i], p2[i] = t;
            }
        }
    }

    if (req_comp && req_comp != target) {
        out = convert_format(out, target, req_comp, s->img_x, s->img_y);
        if (out == NULL) return out; // convert_format frees input on failure
    }

    *x = s->img_x;
    *y = s->img_y;
    if (comp) *comp = target;
    return out;
}

#ifndef STBI_NO_STDIO
stbi_uc *stbi_bmp_load             (char const *filename,           int *x, int *y, int *comp, int req_comp)
{
    stbi_uc *data;
    FILE *f = fopen(filename, "rb");
    if (!f) return NULL;
    data = stbi_bmp_load_from_file(f, x,y,comp,req_comp);
    fclose(f);
    return data;
}

stbi_uc *stbi_bmp_load_from_file   (FILE *f,                  int *x, int *y, int *comp, int req_comp)
{
    stbi s;
    start_file(&s, f);
    return bmp_load(&s, x,y,comp,req_comp);
}
#endif

stbi_uc *stbi_bmp_load_from_memory (stbi_uc const *buffer, int len, int *x, int *y, int *comp, int req_comp)
{
    stbi s;
    start_mem(&s, buffer, len);
    return bmp_load(&s, x,y,comp,req_comp);
}

// Targa Truevision - TGA
// by Jonathan Dummer

static int tga_test(stbi *s)
{
    int sz;
    get8u(s);        //    discard Offset
    sz = get8u(s);    //    color type
    if( sz > 1 ) return 0;    //    only RGB or indexed allowed
    sz = get8u(s);    //    image type
    if( (sz != 1) && (sz != 2) && (sz != 3) && (sz != 9) && (sz != 10) && (sz != 11) ) return 0;    //    only RGB or grey allowed, +/- RLE
    get16(s);        //    discard palette start
    get16(s);        //    discard palette length
    get8(s);            //    discard bits per palette color entry
    get16(s);        //    discard x origin
    get16(s);        //    discard y origin
    if( get16(s) < 1 ) return 0;        //    test width
    if( get16(s) < 1 ) return 0;        //    test height
    sz = get8(s);    //    bits per pixel
    if( (sz != 8) && (sz != 16) && (sz != 24) && (sz != 32) ) return 0;    //    only RGB or RGBA or grey allowed
    return 1;        //    seems to have passed everything
}

#ifndef STBI_NO_STDIO
int      stbi_tga_test_file        (FILE *f)
{
    stbi s;
    int r,n = ftell(f);
    start_file(&s, f);
    r = tga_test(&s);
    fseek(f,n,SEEK_SET);
    return r;
}
#endif

int      stbi_tga_test_memory      (stbi_uc const *buffer, int len)
{
    stbi s;
    start_mem(&s, buffer, len);
    return tga_test(&s);
}

static stbi_uc *tga_load(stbi *s, int *x, int *y, int *comp, int req_comp)
{
    //    read in the TGA header stuff
    int tga_offset = get8u(s);
    int tga_indexed = get8u(s);
    int tga_image_type = get8u(s);
    int tga_is_RLE = 0;
    int tga_palette_start = get16le(s);
    int tga_palette_len = get16le(s);
    int tga_palette_bits = get8u(s);
    int tga_x_origin = get16le(s);
    int tga_y_origin = get16le(s);
    int tga_width = get16le(s);
    int tga_height = get16le(s);
    int tga_bits_per_pixel = get8u(s);
    int tga_inverted = get8u(s);
    //    image data
    unsigned char *tga_data;
    unsigned char *tga_palette = NULL;
    int i, j;
    unsigned char raw_data[4];
    unsigned char trans_data[4] = {0, 0, 0, 0};
    int RLE_count = 0;
    int RLE_repeating = 0;
    int read_next_pixel = 1;
    //    do a tiny bit of precessing
    if( tga_image_type >= 8 )
    {
        tga_image_type -= 8;
        tga_is_RLE = 1;
    }
    /* int tga_alpha_bits = tga_inverted & 15; */
    tga_inverted = 1 - ((tga_inverted >> 5) & 1);

    //    error check
    if( //(tga_indexed) ||
            (tga_width < 1) || (tga_height < 1) ||
            (tga_image_type < 1) || (tga_image_type > 3) ||
            ((tga_bits_per_pixel != 8) && (tga_bits_per_pixel != 16) &&
             (tga_bits_per_pixel != 24) && (tga_bits_per_pixel != 32))
            )
    {
        return NULL;
    }

    //    If I'm paletted, then I'll use the number of bits from the palette
    if( tga_indexed )
    {
        tga_bits_per_pixel = tga_palette_bits;
    }

    //    tga info
    *x = tga_width;
    *y = tga_height;
    if( (req_comp < 1) || (req_comp > 4) )
    {
        //    just use whatever the file was
        req_comp = tga_bits_per_pixel / 8;
        *comp = req_comp;
    } else
    {
        //    force a new number of components
        *comp = tga_bits_per_pixel/8;
    }
    tga_data = (unsigned char*)malloc( tga_width * tga_height * req_comp );

    //    skip to the data's starting position (offset usually = 0)
    skip(s, tga_offset );
    //    do I need to load a palette?
    if( tga_indexed )
    {
        //    any data to skip? (offset usually = 0)
        skip(s, tga_palette_start );
        //    load the palette
        tga_palette = (unsigned char*)malloc( tga_palette_len * tga_palette_bits / 8 );
        getn(s, tga_palette, tga_palette_len * tga_palette_bits / 8 );
    }
    //    load the data
    for( i = 0; i < tga_width * tga_height; ++i )
    {
        //    if I'm in RLE mode, do I need to get a RLE chunk?
        if( tga_is_RLE )
        {
            if( RLE_count == 0 )
            {
                //    yep, get the next byte as a RLE command
                int RLE_cmd = get8u(s);
                RLE_count = 1 + (RLE_cmd & 127);
                RLE_repeating = RLE_cmd >> 7;
                read_next_pixel = 1;
            } else if( !RLE_repeating )
            {
                read_next_pixel = 1;
            }
        } else
        {
            read_next_pixel = 1;
        }
        //    OK, if I need to read a pixel, do it now
        if( read_next_pixel )
        {
            //    load however much data we did have
            if( tga_indexed )
            {
                //    read in 1 byte, then perform the lookup
                int pal_idx = get8u(s);
                if( pal_idx >= tga_palette_len )
                {
                    //    invalid index
                    pal_idx = 0;
                }
                pal_idx *= tga_bits_per_pixel / 8;
                for( j = 0; j*8 < tga_bits_per_pixel; ++j )
                {
                    raw_data[j] = tga_palette[pal_idx+j];
                }
            } else
            {
                //    read in the data raw
                for( j = 0; j*8 < tga_bits_per_pixel; ++j )
                {
                    raw_data[j] = get8u(s);
                }
            }
            //    convert raw to the intermediate format
            switch( tga_bits_per_pixel )
            {
                case 8:
                    //    Luminous => RGBA
                    trans_data[0] = raw_data[0];
                    trans_data[1] = raw_data[0];
                    trans_data[2] = raw_data[0];
                    trans_data[3] = 255;
                    break;
                case 16:
                    //    Luminous,Alpha => RGBA
                    trans_data[0] = raw_data[0];
                    trans_data[1] = raw_data[0];
                    trans_data[2] = raw_data[0];
                    trans_data[3] = raw_data[1];
                    break;
                case 24:
                    //    BGR => RGBA
                    trans_data[0] = raw_data[2];
                    trans_data[1] = raw_data[1];
                    trans_data[2] = raw_data[0];
                    trans_data[3] = 255;
                    break;
                case 32:
                    //    BGRA => RGBA
                    trans_data[0] = raw_data[2];
                    trans_data[1] = raw_data[1];
                    trans_data[2] = raw_data[0];
                    trans_data[3] = raw_data[3];
                    break;
            }
            //    clear the reading flag for the next pixel
            read_next_pixel = 0;
        } // end of reading a pixel
        //    convert to final format
        switch( req_comp )
        {
            case 1:
                //    RGBA => Luminance
                tga_data[i*req_comp+0] = compute_y(trans_data[0],trans_data[1],trans_data[2]);
                break;
            case 2:
                //    RGBA => Luminance,Alpha
                tga_data[i*req_comp+0] = compute_y(trans_data[0],trans_data[1],trans_data[2]);
                tga_data[i*req_comp+1] = trans_data[3];
                break;
            case 3:
                //    RGBA => RGB
                tga_data[i*req_comp+0] = trans_data[0];
                tga_data[i*req_comp+1] = trans_data[1];
                tga_data[i*req_comp+2] = trans_data[2];
                break;
            case 4:
                //    RGBA => RGBA
                tga_data[i*req_comp+0] = trans_data[0];
                tga_data[i*req_comp+1] = trans_data[1];
                tga_data[i*req_comp+2] = trans_data[2];
                tga_data[i*req_comp+3] = trans_data[3];
                break;
        }
        //    in case we're in RLE mode, keep counting down
        --RLE_count;
    }
    //    do I need to invert the image?
    if( tga_inverted )
    {
        for( j = 0; j*2 < tga_height; ++j )
        {
            int index1 = j * tga_width * req_comp;
            int index2 = (tga_height - 1 - j) * tga_width * req_comp;
            for( i = tga_width * req_comp; i > 0; --i )
            {
                unsigned char temp = tga_data[index1];
                tga_data[index1] = tga_data[index2];
                tga_data[index2] = temp;
                ++index1;
                ++index2;
            }
        }
    }
    //    clear my palette, if I had one
    if( tga_palette != NULL )
    {
        free( tga_palette );
    }
    //    the things I do to get rid of an error message, and yet keep
    //    Microsoft's C compilers happy... [8^(
    tga_palette_start = tga_palette_len = tga_palette_bits =
    tga_x_origin = tga_y_origin = 0;
    //    OK, done
    return tga_data;
}

#ifndef STBI_NO_STDIO
stbi_uc *stbi_tga_load             (char const *filename,           int *x, int *y, int *comp, int req_comp)
{
    stbi_uc *data;
    FILE *f = fopen(filename, "rb");
    if (!f) return NULL;
    data = stbi_tga_load_from_file(f, x,y,comp,req_comp);
    fclose(f);
    return data;
}

stbi_uc *stbi_tga_load_from_file   (FILE *f,                  int *x, int *y, int *comp, int req_comp)
{
    stbi s;
    start_file(&s, f);
    return tga_load(&s, x,y,comp,req_comp);
}
#endif

stbi_uc *stbi_tga_load_from_memory (stbi_uc const *buffer, int len, int *x, int *y, int *comp, int req_comp)
{
    stbi s;
    start_mem(&s, buffer, len);
    return tga_load(&s, x,y,comp,req_comp);
}


// *************************************************************************************************
// Photoshop PSD loader -- PD by Thatcher Ulrich, integration by Nicholas Schulz, tweaked by STB

static int psd_test(stbi *s)
{
    if (get32(s) != 0x38425053) return 0;    // "8BPS"
    else return 1;
}

#ifndef STBI_NO_STDIO
int stbi_psd_test_file(FILE *f)
{
    stbi s;
    int r,n = ftell(f);
    start_file(&s, f);
    r = psd_test(&s);
    fseek(f,n,SEEK_SET);
    return r;
}
#endif

int stbi_psd_test_memory(stbi_uc const *buffer, int len)
{
    stbi s;
    start_mem(&s, buffer, len);
    return psd_test(&s);
}

static stbi_uc *psd_load(stbi *s, int *x, int *y, int *comp, int req_comp)
{
    int    pixelCount;
    int channelCount, compression;
    int channel, i, count, len;
    int w,h;
    uint8 *out;

    // Check identifier
    if (get32(s) != 0x38425053)    // "8BPS"
        return epuc("not PSD", "Corrupt PSD image");

    // Check file type version.
    if (get16(s) != 1)
        return epuc("wrong version", "Unsupported version of PSD image");

    // Skip 6 reserved bytes.
    skip(s, 6 );

    // Read the number of channels (R, G, B, A, etc).
    channelCount = get16(s);
    if (channelCount < 0 || channelCount > 16)
        return epuc("wrong channel count", "Unsupported number of channels in PSD image");

    // Read the rows and columns of the image.
    h = get32(s);
    w = get32(s);

    // Make sure the depth is 8 bits.
    if (get16(s) != 8)
        return epuc("unsupported bit depth", "PSD bit depth is not 8 bit");

    // Make sure the color mode is RGB.
    // Valid options are:
    //   0: Bitmap
    //   1: Grayscale
    //   2: Indexed color
    //   3: RGB color
    //   4: CMYK color
    //   7: Multichannel
    //   8: Duotone
    //   9: Lab color
    if (get16(s) != 3)
        return epuc("wrong color format", "PSD is not in RGB color format");

    // Skip the Mode Data.  (It's the palette for indexed color; other info for other modes.)
    skip(s,get32(s) );

    // Skip the image resources.  (resolution, pen tool paths, etc)
    skip(s, get32(s) );

    // Skip the reserved data.
    skip(s, get32(s) );

    // Find out if the data is compressed.
    // Known values:
    //   0: no compression
    //   1: RLE compressed
    compression = get16(s);
    if (compression > 1)
        return epuc("bad compression", "PSD has an unknown compression format");

    // Create the destination image.
    out = (stbi_uc *) malloc(4 * w*h);
    if (!out) return epuc("outofmem", "Out of memory");
    pixelCount = w*h;

    // Initialize the data to zero.
    //memset( out, 0, pixelCount * 4 );

    // Finally, the image data.
    if (compression) {
        // RLE as used by .PSD and .TIFF
        // Loop until you get the number of unpacked bytes you are expecting:
        //     Read the next source byte into n.
        //     If n is between 0 and 127 inclusive, copy the next n+1 bytes literally.
        //     Else if n is between -127 and -1 inclusive, copy the next byte -n+1 times.
        //     Else if n is 128, noop.
        // Endloop

        // The RLE-compressed data is preceeded by a 2-byte data count for each row in the data,
        // which we're going to just skip.
        skip(s, h * channelCount * 2 );

        // Read the RLE data by channel.
        for (channel = 0; channel < 4; channel++) {
            uint8 *p;

            p = out+channel;
            if (channel >= channelCount) {
                // Fill this channel with default data.
                for (i = 0; i < pixelCount; i++) *p = (channel == 3 ? 255 : 0), p += 4;
            } else {
                // Read the RLE data.
                count = 0;
                while (count < pixelCount) {
                    len = get8(s);
                    if (len == 128) {
                        // No-op.
                    } else if (len < 128) {
                        // Copy next len+1 bytes literally.
                        len++;
                        count += len;
                        while (len) {
                            *p = static_cast<uint8>(get8(s));
                            p += 4;
                            len--;
                        }
                    } else if (len > 128) {
                        uint32    val;
                        // Next -len+1 bytes in the dest are replicated from next source byte.
                        // (Interpret len as a negative 8-bit int.)
                        len ^= 0x0FF;
                        len += 2;
                        val = get8(s);
                        count += len;
                        for ( ; len ; len--) {
                            *p = static_cast<uint8>(val);
                            p += 4;
                        }
                    }
                }
            }
        }

    } else {
        // We're at the raw image data.  It's each channel in order (Red, Green, Blue, Alpha, ...)
        // where each channel consists of an 8-bit value for each pixel in the image.

        // Read the data by channel.
        for (channel = 0; channel < 4; channel++) {
            uint8 *p;

            p = out + channel;
            if (channel > channelCount) {
                // Fill this channel with default data.
                for (i = 0; i < pixelCount; i++) *p = channel == 3 ? 255 : 0, p += 4;
            } else {
                // Read the data.
                count = 0;
                for (i = 0; i < pixelCount; i++) {
                    p[i * 4] = static_cast<uint8>(get8(s));
                }
            }
        }
    }

    if (req_comp && req_comp != 4) {
        out = convert_format(out, 4, req_comp, w, h);
        if (out == NULL) return out; // convert_format frees input on failure
    }

    if (comp) *comp = channelCount;
    *y = h;
    *x = w;

    return out;
}

#ifndef STBI_NO_STDIO
stbi_uc *stbi_psd_load(char const *filename, int *x, int *y, int *comp, int req_comp)
{
    stbi_uc *data;
    FILE *f = fopen(filename, "rb");
    if (!f) return NULL;
    data = stbi_psd_load_from_file(f, x,y,comp,req_comp);
    fclose(f);
    return data;
}

stbi_uc *stbi_psd_load_from_file(FILE *f, int *x, int *y, int *comp, int req_comp)
{
    stbi s;
    start_file(&s, f);
    return psd_load(&s, x,y,comp,req_comp);
}
#endif

stbi_uc *stbi_psd_load_from_memory (stbi_uc const *buffer, int len, int *x, int *y, int *comp, int req_comp)
{
    stbi s;
    start_mem(&s, buffer, len);
    return psd_load(&s, x,y,comp,req_comp);
}


// *************************************************************************************************
// Radiance RGBE HDR loader
// originally by Nicolas Schulz
#ifndef STBI_NO_HDR
static int hdr_test(stbi *s)
{
    char *signature = (char *)"#?RADIANCE\n";
    int i;
    for (i=0; signature[i]; ++i)
        if (get8(s) != signature[i])
            return 0;
    return 1;
}

int stbi_hdr_test_memory(stbi_uc const *buffer, int len)
{
    stbi s;
    start_mem(&s, buffer, len);
    return hdr_test(&s);
}

#ifndef STBI_NO_STDIO
int stbi_hdr_test_file(FILE *f)
{
    stbi s;
    int r,n = ftell(f);
    start_file(&s, f);
    r = hdr_test(&s);
    fseek(f,n,SEEK_SET);
    return r;
}
#endif

#define HDR_BUFLEN  1024
static char *hdr_gettoken(stbi *z, char *buffer)
{
    int len=0;
    char c = '\0';

    c = static_cast<char>(get8(z));

    while (!at_eof(z) && c != '\n') {
        buffer[len++] = c;
        if (len == HDR_BUFLEN-1) {
            // flush to end of line
            while (!at_eof(z) && get8(z) != '\n')
                ;
            break;
        }
        c = static_cast<char>(get8(z));
    }

    buffer[len] = 0;
    return buffer;
}

static void hdr_convert(float *output, stbi_uc *input, int req_comp)
{
    if( input[3] != 0 ) {
        float f1;
        // Exponent
        f1 = (float) ldexp(1.0f, input[3] - (int)(128 + 8));
        if (req_comp <= 2)
            output[0] = (input[0] + input[1] + input[2]) * f1 / 3;
        else {
            output[0] = input[0] * f1;
            output[1] = input[1] * f1;
            output[2] = input[2] * f1;
        }
        if (req_comp == 2) output[1] = 1;
        if (req_comp == 4) output[3] = 1;
    } else {
        switch (req_comp) {
            case 4: output[3] = 1; /* fallthrough */
            case 3: output[0] = output[1] = output[2] = 0;
                break;
            case 2: output[1] = 1; /* fallthrough */
            case 1: output[0] = 0;
                break;
        }
    }
}


static float *hdr_load(stbi *s, int *x, int *y, int *comp, int req_comp)
{
    char buffer[HDR_BUFLEN];
    char *token;
    int valid = 0;
    int width, height;
    stbi_uc *scanline;
    float *hdr_data;
    int len;
    unsigned char count, value;
    int i, j, k, c1,c2, z;


    // Check identifier
    if (strcmp(hdr_gettoken(s,buffer), "#?RADIANCE") != 0)
        return epf("not HDR", "Corrupt HDR image");

    // Parse header
    while(1) {
        token = hdr_gettoken(s,buffer);
        if (token[0] == 0) break;
        if (strcmp(token, "FORMAT=32-bit_rle_rgbe") == 0) valid = 1;
    }

    if (!valid)    return epf("unsupported format", "Unsupported HDR format");

    // Parse width and height
    // can't use sscanf() if we're not using stdio!
    token = hdr_gettoken(s,buffer);
    if (strncmp(token, "-Y ", 3))  return epf("unsupported data layout", "Unsupported HDR format");
    token += 3;
    height = strtol(token, &token, 10);
    while (*token == ' ') ++token;
    if (strncmp(token, "+X ", 3))  return epf("unsupported data layout", "Unsupported HDR format");
    token += 3;
    width = strtol(token, NULL, 10);

    *x = width;
    *y = height;

    *comp = 3;
    if (req_comp == 0) req_comp = 3;

    // Read data
    hdr_data = (float *) malloc(height * width * req_comp * sizeof(float));

    // Load image data
    // image data is stored as some number of sca
    if( width < 8 || width >= 32768) {
        // Read flat data
        for (j=0; j < height; ++j) {
            for (i=0; i < width; ++i) {
                stbi_uc rgbe[4];
                main_decode_loop:
                getn(s, rgbe, 4);
                hdr_convert(hdr_data + j * width * req_comp + i * req_comp, rgbe, req_comp);
            }
        }
    } else {
        // Read RLE-encoded data
        scanline = NULL;

        for (j = 0; j < height; ++j) {
            c1 = get8(s);
            c2 = get8(s);
            len = get8(s);
            if (c1 != 2 || c2 != 2 || (len & 0x80)) {
                // not run-length encoded, so we have to actually use THIS data as a decoded
                // pixel (note this can't be a valid pixel--one of RGB must be >= 128)
                stbi_uc rgbe[4] = { (stbi_uc)c1, (stbi_uc)c2, (stbi_uc)len, (stbi_uc)get8(s) };
                hdr_convert(hdr_data, rgbe, req_comp);
                i = 1;
                j = 0;
                free(scanline);
                goto main_decode_loop; // yes, this is fucking insane; blame the fucking insane format
            }
            len <<= 8;
            len |= get8(s);
            if (len != width) { free(hdr_data); free(scanline); return epf("invalid decoded scanline length", "corrupt HDR"); }
            if (scanline == NULL) scanline = (stbi_uc *) malloc(width * 4);

            for (k = 0; k < 4; ++k) {
                i = 0;
                while (i < width) {
                    count = static_cast<uint8>(get8(s));
                    if (count > 128) {
                        // Run
                        value = static_cast<uint8>(get8(s));
                        count -= 128;
                        for (z = 0; z < count; ++z)
                            scanline[i++ * 4 + k] = value;
                    } else {
                        // Dump
                        for (z = 0; z < count; ++z)
                            scanline[i++ * 4 + k] = static_cast<stbi_uc>(get8(s));
                    }
                }
            }
            for (i=0; i < width; ++i)
                hdr_convert(hdr_data+(j*width + i)*req_comp, scanline + i*4, req_comp);
        }
        free(scanline);
    }

    return hdr_data;
}

#ifndef STBI_NO_STDIO
float *stbi_hdr_load_from_file(FILE *f, int *x, int *y, int *comp, int req_comp)
{
    stbi s;
    start_file(&s,f);
    return hdr_load(&s,x,y,comp,req_comp);
}
#endif

float *stbi_hdr_load_from_memory(stbi_uc const *buffer, int len, int *x, int *y, int *comp, int req_comp)
{
    stbi s;
    start_mem(&s,buffer, len);
    return hdr_load(&s,x,y,comp,req_comp);
}

#endif // STBI_NO_HDR

/////////////////////// write image ///////////////////////



static void write8(FILE *f, int x) { uint8 z = (uint8) x; fwrite(&z,1,1,f); }

static void writefv(FILE *f, char *fmt, va_list v)
{
    while (*fmt) {
        switch (*fmt++) {
            case ' ': break;
            case '1': { uint8 x = va_arg(v, int); write8(f,x); break; }
            case '2': { int16 x = va_arg(v, int); write8(f,x); write8(f,x>>8); break; }
            case '4': { int32 x = va_arg(v, int); write8(f,x); write8(f,x>>8); write8(f,x>>16); write8(f,x>>24); break; }
            default:
                assert(0);
                va_end(v);
                return;
        }
    }
}

static void writef(FILE *f, char *fmt, ...)
{
    va_list v;
    va_start(v, fmt);
    writefv(f,fmt,v);
    va_end(v);
}

static void write_pixels(FILE *f, int rgb_dir, int vdir, int x, int y, int comp, void *data, int write_alpha, int scanline_pad)
{
    uint8 bg[3] = { 255, 0, 255}, px[3];
    uint32 zero = 0;
    int i,j,k, j_end;

    if (vdir < 0)
        j_end = -1, j = y-1;
    else
        j_end =  y, j = 0;

    for (; j != j_end; j += vdir) {
        for (i=0; i < x; ++i) {
            uint8 *d = (uint8 *) data + (j*x+i)*comp;
            if (write_alpha < 0)
                fwrite(&d[comp-1], 1, 1, f);
            switch (comp) {
                case 1:
                case 2: writef(f, "111", d[0],d[0],d[0]);
                    break;
                case 4:
                    if (!write_alpha) {
                        for (k=0; k < 3; ++k)
                            px[k] = bg[k] + ((d[k] - bg[k]) * d[3])/255;
                        writef(f, "111", px[1-rgb_dir],px[1],px[1+rgb_dir]);
                        break;
                    }
                    /* FALLTHROUGH */
                case 3:
                    writef(f, "111", d[1-rgb_dir],d[1],d[1+rgb_dir]);
                    break;
            }
            if (write_alpha > 0)
                fwrite(&d[comp-1], 1, 1, f);
        }
        fwrite(&zero,scanline_pad,1,f);
    }
}

static int outfile(char const *filename, int rgb_dir, int vdir, int x, int y, int comp, void *data, int alpha, int pad, char *fmt, ...)
{
    FILE *f = fopen(filename, "wb");
    if (f) {
        va_list v;
        va_start(v, fmt);
        writefv(f, fmt, v);
        va_end(v);
        write_pixels(f,rgb_dir,vdir,x,y,comp,data,alpha,pad);
        fclose(f);
    }
    return f != NULL;
}

int stbi_write_bmp(char const *filename, int x, int y, int comp, void *data)
{
    int pad = (-x*3) & 3;
    return outfile(filename,-1,-1,x,y,comp,data,0,pad,
                   "11 4 22 4" "4 44 22 444444",
                   'B', 'M', 14+40+(x*3+pad)*y, 0,0, 14+40,  // file header
                   40, x,y, 1,24, 0,0,0,0,0,0);             // bitmap header
}

int stbi_write_tga(char const *filename, int x, int y, int comp, void *data)
{
    int has_alpha = !(comp & 1);
    return outfile(filename, -1,-1, x, y, comp, data, has_alpha, 0,
                   "111 221 2222 11", 0,0,2, 0,0,0, 0,0,x,y, 24+8*has_alpha, 8*has_alpha);
}